Tuesday, 26 August 2014

Open to Interpretation: review of "Misquoting Muhammad".

The subtitle of the book highlights "The Challenge and Choices of Interpreting the Prophet's Legacy", and it was the Choices element that most interested me in this lucid and interesting history of competing traditions of interpretation within Sunni Islam.  The array of choices around interpretation gave me the impression of epistemological vertigo.  It makes sense of why almost anything that can be said about Islam seems to be immediately subject to debate.

Again and again, Brown points up choices that have had to be made between interpretative strategies in order to work out what implications for Sharia law to take from the Qur'an and Muhammad's recorded sayings and conduct.  For any given statement in the Qur'an, or about the prophetic Sunna as recorded in the Hadith literature, one might ask, for example:
  • Is the statement an imperative command, or something else, like an expression of mere opinion, or hyperbole, or factual observation?
  • Is the statement of general validity or limited to specific circumstances, historical or moral?
  • If so, what is the appropriate context for understanding it?
  • If the statements comports awkwardly with another statement, does one complement the other, or specify it, or abrogate it, and if so which controls the other?
  • If the statement is drawn from a hadith, is it authentic in origin and reliable in transmission?  (On which see this fascinating chapter of Brown's previous interesting book.)
This is just a small selection of the ramifying interpretative questions that lead off into a maze of competing theories.

Here is a first example of the dizzying uncertainty of it all.  Sura 2:282 reads in part:
O you who have believed, when you contract a debt for a specified term, write it down. ... And bring to witness two witnesses from among your men. And if there are not two men, then a man and two women from those whom you accept as witnesses - so that if one of the women errs, then the other can remind her.
So, at a minimum, Muhammad is held to have prophesied from God that two women were required to replace one man as a witness to a debt, due to the risk of a female deficit of memory.  But just at that time, or forever?  Just there or everywhere?  Does the same requirement apply to other matters of testimony?

One sees the questions ramify as Brown lays out various sides to the interpretative debate over the implications of this statement:
While the majority of Sunni schools understood this as meaning that women could only bear witness in cases concerning financial transactions, and even then carrying only half the evidentiary value of a man, the Hanafi school held that they were fundamentally sound witnesses and could thus testify in other matters such as marriage, divorce, inheritance and even manslaughter.
So there was debate about whether the Quranic requirement for two women to testify about debt excluded women witnessing to other matters, or else included them as witnesses in other matters so that they could testify in the same way as men on those.
Ghazali stepped even further than his Hanafi school on this matter. [He] deemed the reasons for which God had treated female witnesses differently than males to be obsolete. He understood the Qur’an’s commandment on witnessing to be premised on a world where women had little commercial experience. In the modern world, in which women ran corporations, the reason behind the Qur’anic laws no longer applied.
So there was also debate about whether the statement applied generally for all time, or only in the historical circumstances of Muhammad's world.
[O]ne scholar of Mecca had written that, even if the Prophet’s wife Aisha herself came to bear witness in court, her sole testimony would not be accepted. This despite the fact that many of the rulings of the Shariah itself were established by Hadiths that Aisha alone narrated from the Prophet. Any inconsistency that we sense in such matters comes merely from our inability to grasp the ‘divine secrets’ of God’s justice, the Meccan scholar wrote.
And, furthermore, there were implications to consider about the reputation of Aisha as a transmitter of authoritative tradition, raising the danger of a contradictory attitude towards the reliability of a woman's memory.

In other words, it seems to me, the authoritative statement on the issue of female witnesses was so laconic that it was scarcely able to constrain the scope of debatable implications that it gave rise to.  When so many questions can be asked that cannot be definitively answered, the prophetic authority seems to evaporate in a cloud of questions.

To take another issue, let us consider the prophetic theory of the Just War.  As Brown notes, a medieval consensus accepted that the "Sword verses" of Sura 9 abrogated (replaced) all previously revealed "principles of proportionality and non-aggression", so that:
Jihad for the expansion of the Abode of Islam thus became a collective duty for the Muslim polity according to all Sunni schools of law. ... Jihad was understood as the unceasing quest to ‘make God’s word supreme,’ as Hadiths described, through the ongoing expansion of the rule of God’s law on earth.
That is, all Sunni schools of law accepted a conclusion for centuries following the establishment of Islam that virtually all Sunni ulema now repudiate.  If it is possible to take the same set of authoritative sources, and yet derive at two points in time two such radically opposite consensuses of expert jurists on the same vital question, then one must ask whether the supposedly authoritative, prophetic sources provide any firm guidance at all on the matter.

Even seemingly plain statements of legislation fizzle into a web of questions and contexts and extrapolations, such as around the question:
‘How should a thief who has stolen loaves of bread from a baker be punished?’ Abu Hanifa and the young scholars who congregated around him would look first to the Qur’an. It states clearly, ‘The thief, male or female , cut off their hand as a punishment for what they have earned…’ (5: 38). But Abu Hanifa would also remember that his teacher Hammad had heard the great Nakha‘i tell that the Prophet only ordered this punishment if the item stolen was worth more than ten silver coins. Moreover, earlier Kufan masters had ruled, on the basis of a well-known Hadith from the Prophet, that ‘There is no amputation for stealing the fruits [of a palm tree] or its heart.’ But Abu Hanifa and his colleagues would still not have found a clear answer to the question of the loaves of bread in the Qur’an, the Hadiths or the Companion rulings at their disposal. How could they use these sources to cover new territory and resolve the question?
Abu Hanifa developed a systematic form of analogical reasoning, called Qiyas, to extend the ruling of one situation to another based on a shared legal cause (‘illa) – that feature for which God or the Prophet had judged the situation in a certain way. By understanding what lay behind the rulings of the Qur’an and Hadiths, these rulings could be extended to unknown situations that shared the same legal causes. Abu Hanifa understood that the Prophet had ruled out the severe punishment of amputating a hand for stealing the yield of a palm tree because the fruit would soon rot anyway. It was too ephemeral to merit such a harsh response. He thus concluded that the theft of any foodstuff, such as a loaf of bread, that would quickly rot would not entail losing a hand.
Of course, Qiyas was a precarious process. The Qur’an and Hadiths rarely explained clearly the legal cause of a ruling, and it was left to scholars like Abu Hanifa to derive it from context. Some disagreed with his Qiyas in the case of date palms, arguing that the reason the Prophet had prohibited amputating a hand for stealing dates from trees was that in Medina such exposed fruit was considered semi-public property.
More importantly, there may be no reason at all for a ruling...
What makes the question so vertiginous here, is that no sooner do we find a clear ruling in the Qur'an on the punishment of a thief, than other rulings brought in from the Sunna of Muhammad fog up the picture.

So somebody reported that Muhammad only punished by mutilation thefts to a value greater than 10 silver coins.  One can imagine the ramifying questions: Did this report characterise Muhammad's decisions before or after the revelation of the punishment of thieves in Sura 5?  Was it authentic and reliable?  Is the ten-silver-coins test to be applied in nominal or real terms today?  Was Muhammad's laxity towards lesser thefts due to his mercy or his justice?  Was it his peculiar way or a general rule?  What about the palm-fruit exception?  Was this exempted because it would soon rot, or because it was so cheap, or because it was common property?  Or because of local custom in Medina?  Or because of a combination of such factors?

Who knows?  One can imagine a range of implications being drawn.  For every debatable point in a statement there are at least two interpretative options, and when you multiply these together, they multiply out to many different interpretations even of apparently simply points.  This is without even taking into account the problem that there might be a divine ruling made a certain way for no apparent reason.

And that is where this book ultimately leaves me, with the feeling that Islam is so open to interpretation that its adherents have great leeway in deriving implications from its sources of authority, and that while little is definitively mandated, by the same token much seems not to be definitively ruled out.  This may be a bias of the author's focus on differences in interpretation rather than commonalities, but on the other hand his examples cover a huge spread of issues.

My final, more personal conclusion is summed up by Brown's lengthy discussion of how many scholars have tried to interpret away the Qur'an's apparent permission for husbands to strike their wives.  They seem to have tried every interpretative strategy to generate the result they seek.  It is not easy, though, to find an acceptable meaning for the verb in question that makes sense of the Hadith saying that if husbands strike their wives then it may be only "with a light blow that leaves no mark."  This verse, for one, seems to be an indisputable permission, albeit in however limited circumstances, to use violence.  Yet, having found an island of clarity, many believers go out of their way to reject it.

Surely the reason why so many Muslims, like people everywhere, regard hitting people as wrong and in fact disallowed in all but the most necessary circumstances, is that they derive their sense of right and wrong from their wider culture.  I do not believe that most Muslims' rejection of wife-beating is due to the "well-established precedent of the Prophet’s treatment of wives and his strong criticism of striking women" which Brown states has been the main scholarly justification for seeking to interpret the Qur'an in such a way as to prevent it from recommending what it appears to recommend.  I cannot believe that millions of people are so devoid of personal conscience that they would not know whether to think hitting people was right or wrong without the benefit of a sanctified model human being.  They might argue that they derive fundamental values from their religion which seem to be at odds with specific texts, but even then they are making their own judgement as to which values are so fundamental as to override the plain meaning of the texts they dislike.

When they go picking and choosing values and interpretations, they are starting from the same place as I, an atheist, do.  Once you are seeking as much leeway as you can possibly get to force through your preferred interpretation, because you don't want your scripture to say what it says, then you may as well give up taking prophetic and scriptural authorities as your guide.

So Muslims (like Jews, who have a similarly huge and multiplicitous body of authoritative sources) seem to have two choices: either seek to take their moral code from their religion's authoritative sources, in which case their guidance seems in many cases hopelessly indefinite; or else start out from their own moral sense and seek to have it confirmed in the sources, in which case confirmation really adds nothing at all.  It's like an empirical version of the Euthyphro Problem, in which Socrates posed a fundamental and unanswered dilemma for religious ethics.  Whichever horn you choose to sit on, the notion that religion provides a clearer and more rigorous moral code than atheists can hold takes a big hit.

Thursday, 21 August 2014

"My model of your model of my mind is consciousness." Review of 'Unthink'.


This is a very intriguing short book about your consciousness and unconsciousness.  It is deeply rooted in experimental findings rather than armchair philosophising, but also very readable.  It's one of those funny coincidences that I was drawn to it on the library's shelves of new acquisitions, given how I blogged on the topic yesterdayOr was it?!

In the first two chapters, Paley summarises a huge pile of studies in experimental psychology that go to prove how "the unconscious does what the conscious thinks the conscious does".  He gives potted accounts of many studies of circumstances which were found to affect subjects' memories and decisions without them consciously knowing it.

Witnesses to a video car-crash more often misreported seeing broken glass when they were asked about the cars that smashed into each other than when asked about cars that bumped.  Subjects did not realise they more often chose Dasani branded water based on product-placing they could not consciously recall noticing.  Academic psychologists learned to do better at a seemingly randomised computer game without knowing they had learned anything at all.  What you consciously hear can be changed by what your eyes see.  Subjects holding pens between their lips so they can't smile think a cartoon is less amusing than subjects holding pens between their teeth.  Shoppers have a bias towards goods on the right-hand side of a stall, yet they explain their preference in terms of the quality of the goods, even when all the goods are identical.  And so on and on.

The most interesting experimental finding which was new to me, was that autistic children who fail to appreciate that other people can have false beliefs, also fail to appreciate that they themselves previously held a false belief.  In other words, their theory-of-mind or mind-reading faculty that malfunctioned when turned outward on other people also malfunctioned when turned in on themselves, as if the same faculty that interprets the minds of others also interprets our own.  That is huge.  (Reference - pdf.)

There is a brain-zapping experiment with a Transcranial Magnetic Stimulation wand that I won't get into, and a very persuasive experiment on somebody with their brain hemispheres disconnected.  (I should probably check out some of these studies for myself, because the relentless flood of findings is highly persuasive.)  Paley's evidence bears out his statement:
If consciousness determined our behaviour we'd already know that was how we worked; but as it doesn't, we don't.
The next question is, "Why do we have the conscious impression that we know why and what we are doing?"  Why do we "infer a decision to act from the fact that we have acted"?  Why do conscious minds bother to do this?

Paley's theory is interesting (although I can't tell you how original it is).  To summarise it in my own words, he proposes that, just as we have a theory-of-mind program running in our minds that models the minds of other people, so we model our own minds in the same way.  This lets us know how other people might be modelling our minds.  Which let's us predict how they will respond to our actions, since their reactions depend on their assessment of our motives.  And if we can predict how they will respond to us, then we can better manipulate them and thus acquire a selective advantage that will promote the development and spread of consciousness as an adaptation.

As Paley puts it:
The role of consciousness is to explain plausibly why we made the decision we did in the way that someone else (with an equal lack of knowledge about how decisions are really made) might also explain our choices.
And:
 Our conscious model of our self is primarily for adjusting how we are perceived.
The evolutionary logic is intriguing.  As a higher animal evolved a theory-of-mind faculty for modelling in its own mind the beliefs and intentions of its conspecifics, there would be a corresponding selective pressure for any given individual to model those conspecifics' models of its own mind.  How better to do this than by reflexively applying the theory-of-mind faculty to the behaviour of the individual itself—even though, nay because, this would imply turning the faulty, misperceiving interpreting faculty back on oneself?
My model of your model of my mind is consciousness.
This would neatly explain why a conscious human mind does not accurately model the mind's own knowledge and motivations, but rather interprets and models itself as if from the outside.  That is, as if it were an outsider.  Consciousness should be as bad a mind-reader as the externally directed theory-of-mind faculty.  (Why the theory-of-mind faculty evolved to be inefficient I will leave for another day, but it's another vital question.)

The theory makes sense on the face of it.  It is almost shockingly, simply, right as an explanation of the evidence.  It raises questions, but I think Paley's answers are cogent.

If the function of consciousness is to model one's mind like an outsider does, then why does the conscious mind also receive internal experiences of vision, hearing, taste, warmth, pain, and so on?  Consciousness of sensation would seem to be a whole other area of conscious life that Paley's theory-of-mind theory fails to cater for.

Now, people with brain-damage that has caused them to have "blindsight" can perform visual tasks, as Paley says, better than chance without consciously sensing anything visual, and without being able to consciously explain how they are getting tasks right.  So consciousness is not necessary to vision, just as one would expect it is not (cf. a robot with a camera).  Then why present a visual experience to the conscious mind at all?
 

Paley's answer is that sensory data needs to be reflexively mind-read because it is often sensorily accessible to other minds tooin the sense that an outsider models whether you are seeing what they can seeand so has to be incorporated into one's model of their model of your mind.  We have consciousness of the aspects of our minds that are important to other people.  This is a clever extension of the mind-reading theory to accommodate what seemed at first glance to be a separate domain of conscious experience.  Paley supports it with evidence from various experiments showing, for example, that subjects can be fooled into thinking they are simply drawing a straight line on a computer screen, when in fact they are adjusting to keep the line straight as the computer subtly rotates its output compared with their movement.  The subjects accept what they can see happening over the signals coming from their own body.

It is not a great step to see that a strategic theory-of-mind ought to know what information its own mind has that other minds lack.  This could explain why consciousness includes access to our long-held memories as well as contemporary sensations.  Not just because they are helpful for developing a more exact theory-of-mind, but in order to make use of the fact that you know things that other minds do not.  Paley's theory seems to work.

However, one thing Paley's theory does not really do is to get us any further on the Hard Problem of consciousness, i.e. why we have internal, subjective experiences of anything at all.  Could not a faculty as unconscious as that which makes our decisions for us also handle representation of what other people construe our minds as thinking?  Maybe I am asking too much, and Paley is for the vast majority of the book not trying to answer the Hard Problem.  He has a theory of what consciousness if for, not of what it is, or of how it arises from dumb matter.  In not attacking the Hard Problem, he fails to solve what I think most people would regard as the greater mystery of the thing.  But I can hardly criticise him for not answering a different question from the one he seemingly set himself.

He does make a brief sally against the Hard Problem, though:
The abstract states of emotions, desires, field of vision, etc., which perhaps only exist in our self-model, are naturally experienced.  We do not think that there is a need to presume a gap between having these states and being conscious of them.  They are our experience.
I think that is equivalent to saying: conscious sensations just are subjectively experienced.  Which is not really a theory at all as to how they arise.  Not that anybody else has ever done any better!

I don't want to finish on a note of disappointment, though.  It seems to me that Paley has done a great service in publishing a theory of what consciousness is for that is derived so deeply from experimental findings rather than armchair philosophising.  Read it.

Wednesday, 20 August 2014

Artificial minds, artificial consciousness

I am reading this rather dated but highly entertaining and informative book on future technologies that may or may not cross from science-fiction into science-fact, and the eccentric people who conceived and promoted them up to 1990.  Things like space-colonies, cryogenics, and nano-tech, but also more interestingly to me things like uploading human minds onto silicon-chips.  I have to say, that although the book is 23 years old, the technologies it talks about still seem very far from realisation!  Some of the ideas are so technophilic, it's creepy.  Such as Hans Moravec's dream of uploading his mind into a "bush-robot", that is, a robot with a plethora of so many branching appendages, of every size and kind down to nano-manipulators, that it would have omnipotent control over its environment.  Who would want to be that robot?

A lot of these futurological and transhumanist ideas really do seem very close to religious ideas.  Conceiving of the self as a pattern of information derived from the mind that can be embodied in any suitable material or body from brain-flesh to silicon-chips, and have a continuing existence independent of any particular incarnation, at last makes sense of the concept of the soul.  It's transmission and deathlessness make sense at last of transmigration and eternal life.  Nanotechnology makes sense of omnipotence, artificial super-intelligence of omniscience.  The transhumanists come across as wacky, but it can hardly be denied that they make much more rational sense of their spiritual impulses than any old-fashioned metaphysical religion can say.

It is a very thought-provoking book, though, especially about ideas to do with artificial minds and intelligences.  (There is also a very interesting new book on the apparent risks of developing artificial super-intelligence.)  The particular questions it is provoking in me at the moment are about what a mind is, and whether an artificial mind could gain consciousness.  Here is an example of something provoking on the subject of uploading your mind:
The theory was, even though you're inside a computer you could still have exactly the same experiences you'd been having in your old body.  The only difference would be, now you'd be experiencing a simulation of reality rather than reality itself.  Or perhaps it would be more accurate to say that you'd be experiencing a different kind of simulation of reality, because as far as Moravec was concerned, that's all your original body ever gave you: a simulation, a mental construct that the brain put together out of the data conveyed to it by the senses.
Here's where my thinking is...

I have NetLogo on my computer.  It's free to download.  You can use it to simulate all sorts of "agent-based" scenarios and see emergent phenomena develop before your eyes.  It comes with lots of free scenarios to play around with.  There is a very effective butterfly-evolution game.  The game starts up by scattering a load of randomly coloured butterflies across a photo of a landscape.  Every time you "catch" a butterfly by clicking on it, that individual is removed, but one randomly selected member of the remaining butterflies spawns an offspring.  That offspring is mutated in colour a certain degree from its parent, and it spawns a certain distance from ityou can play with the parameters.  What happens is, you catch the obvious butterflies easily, and in doing so spawn new offspring that are close in colour to the less obvious bugs.  After a short while, you really cannot see any butterflies at all.  You have caught all the visible ones and the rest are hiding, having inherited their camouflaging colour from the survivors you missed out.

Here they are, obvious to start with:


Here they are, evolved into camouflaged invisibility:


Here's where they are, highlighted out of their hiding-places by the program:


It's fun.  But the point I want to make about them is, that this is real evolution.  It's not a simulation.  There is replication (offspring from survivors), there is mutation (of colour), there is selection (by predation).  There is a genetic code (a string of code determining colour) that is replicated with mutation.  I don't think this is a particularly controversial claim.  The genetic code for butterfly coloration undergoes actual evolution.  It's not a simulation.  (What would a simulation of this process involve?)

Is it artificial life?  Is it life?  If not, why not?

Anyway, what the computer-butterflies definitely don't have is any mind or intelligence, right?  The butterflies do not absorb, process, or act on any information.  They just disappear or spawn.  It's only their removal and replication that process information.

But then, why not conceive of the set of butterflies as an artificial super-organism, deathless (until you shut it down), each butterfly a cell?  Is this not life?  Why not?  It retains itself in existence from moment to moment by maintaining a certain disposition of ones and zeros.  Is that so different from holding onto life and existence by maintaining a certain disposition of homeostatic and thermodynamic properties in the cells and space of your body?  I don't know that it is.

On to minds.  There are other games with bugs that each do information-processing and react to their environment.  These ants (red) come out of the nest (purple) searching for food (blue).  When they are carrying food they emit pheromones (green) that fade over time.  When an ant walks over the pheromone plume, he keeps walking within the plume, often finding the food as he does so.  It is a very simple version of how ants recruit each other to exploit food-sources.


In this simulation, there is clearly mind at work, there is information-processing.  Unlike the butterflies, there is information-processing performed by the program attached to each ant: when it senses pheromone it adjusts its movement.  My question is, is that a simulated mental process, simulated mindor is it mind itself?  There is detection of stimulus (by a computer of a pattern embodied in digital ones and zeros) and reaction (execution of a different pattern than otherwise).  What more can you ask of a thing for it to be a mind?  In very basic, minimal form, this is a replica of the information-processing performed by an ant's mind, embodied in electrical and chemical changes in its brain.

Not a simulation, a replica.  Think back to the quotation about Moravec's thinking:
Or perhaps it would be more accurate to say that you'd be experiencing a different kind of simulation of reality, because as far as Moravec was concerned, that's all your original body ever gave you: a simulation, a mental construct that the brain put together out of the data conveyed to it by the senses.
If an ant's brain is an electro-chemical computer that processes and reacts to sensory input, then what fundamental difference does it make whether those inputs are stimulated by chunks of actual food or ones and zeros interpreted by the programme as chunks of food?  Either way, the brain receives sensory input, processes it, outputs reaction.  Even if the food is simulated, the input and output are the same thing.  The environment may be simulated, but the mind is replicated.  The mind is a real one.

Imagine scanning an ant's brain to gain total knowledge of the disposition and connections of its neurons, then instantiating them in silicon, then hooking that silicon brain back up to the original ant's antennae and legs and jaws.  That would be a real mind, right?  It would be receiving sensory input from the world, and outputting commands to the motor functions.  The ant would go on living its life as before.  So what difference then whether the stimulation of this silicon mind is provided by the real world or a simulated one?  None.

Just as an ant's brain would not cease to embody a real mind just because you stimulated it with electrodes instead of reality, so, by the same token, a silicon mind would not cease to be a real mind because it was stimulated by ones and zeros.  In which case, I think it is quite plain that the computer program provides each ant with a mind instantiated in silicon.  Not a simulated mind, but an artificial mind, which is a kind of real mind.

Now, Is there anything a human or higher-animal mind can do that an artificial mind cannot?  An artificial mind can know, learn, adapt and react.  It can run in different modes which parallel emotional states: imagine a chess computer that goes all-out to capture its opponent's queen if it loses it own.  Is this not the information-processing equivalent of the emotion of desire for immediate revenge against the opposing queen that might motivate a human player?  It might even be an irrational show of emotion that worsens the computer's chance of winning the game in the end.  Why not programme a computer program with any number of such "emotional" modes?

I think the two most prominent doubts over whether computers could perform like a human mind would concern creativity and consciousness.  Creativity I don't want to get into here, because I'm not best sure just what it is.  So consciousness it is.  I mean the subjective feeling possessed by a mind of what it is like to be a mind, or at least the subjective feeling of what the mind presents to the conscious part of itself.  Something like that.

My point on this is simple.  If you are a philosophical naturalist, and believe that the human mind is completely embodied in the human brain, being an information-processing organ that operates according to the laws of nature, then you know that an electro-chemical information-processing machine is capable of producing consciousness.  Something about the material structure of the brain gives rise to consciousness.  Therefore, it follows, any artificial brain that had an equivalent structure, no matter in what kind of material it was instantiated, would also give rise to consciousness.  As long as that equivalency could indeed be realised.  And if it is the information-processing architecture of the brain that matters, rather than, say, something about organic cells, for producing consciousness, then any equivalent information-processing architecture, instantiated in man-made electronics and chemistry, will also produce consciousness.

So if you build a computer that does whatever it is the brain does that gives rise to consciousness, then you will have created artificial consciousness (obviously).  Since the brain can do it, I find it unlikely that a computer cannot do it in principle.  In which case, it seems plain that, if science could continue to make discoveries for long enough, it would be possible to construct not just artificial, real minds, but artificial, real consciousness.

Finally, if a computer can really be conscious, and if Moravec is right in equating the simulation your brain produces of the real world and the simulation it would produce of an artificial world inside a computer, then we have to accept that a mind living inside a computer simulation could be living an equivalently real life to the rest of us, and consciously.  It just would not be living it in the real world.

Like me, somebody will say... ;)

Saturday, 16 August 2014

Bayesian probability analysis of the guilty verdict against Megrahi for the Lockerbie bombing

In my first post about the Lockerbie bombing, I discussed Morag Kerr's book reconstructing the commission of the Lockerbie bombing and demonstrating the innocence of the convicted man, Abdelbaset al-Megrahi.  In common with most humanistic reasoning, neither the verdict that condemned him nor Kerr's argument for his exoneration deployed any arithmetic of probability in analysing the evidence.  I think the widespread lack of arithmetical analysis of evidence is a serious weakness in fields like criminal law and history.

In this, I am following Richard Carrier in his book Proving History.  I am persuaded by him that we ought not just to use adjectives like "possible" and "probable" when we debate which theories best explain the evidence before us on a contentious historical or forensic question.  Additionally, we should use Bayes' Theorem: using numbers to express our opinions, and multiplying and dividing them according to Bayes' formula in order to calculate our reckoning of which theory explains the evidence the best.  The three main virtues of Bayes' Theorem are that it forces the analyst of evidence to specify clearly how good they think a theory is at explaining the evidence; it enables them to put all the evidence together in a mathematically sound way; and, above all, it forces them to look for evidence that supports their theory better than alternative theories, thus helping them to overcome the common failure to give alternatives due consideration.  Of course, different people can have different opinions about probabilities: the virtue of Bayes is that it brings out exactly what people agree and disagree about, and thus focuses their debate productively on crucial areas of disagreement.

Here is a simple account of how to use Bayes' Theorem:
  • We shall test the evidence for theory T (i.e. Megrahi committed the crime) by comparison with theory Not-T or ~T (i.e. Megrahi did not commit the crime).
  • Firstly, we determine the prior probability of T being true.  This is the probability that T is true based simply on our background beliefs; that is, based on general knowledge we have before we start to consider the specific details of the case.  E.g. in general, how probable is it that a bomb in a suitcase could be loaded at Malta?  How probable is it that a bomb could evade detection while undergoing x-ray checks at Frankfurt and Hamburg?
  • Next, we take each piece of specific evidence in turn and consider for each piece its conditional probability of existing if, firstly, T is true, and if, secondly, ~T is true.  E.g. how probable is it that Megrahi would be present at Luqa airport on the day of the bombing if he were not there to load the bomb into the baggage system?  How probable is it that a mysterious piece of unaccompanied baggage would have passed through Frankfurt airport's baggage transfer system, if it were not the bomb-case hypothetically loaded in Malta?
  • For each of T and ~T, we multiply the probabilities of each piece of evidence existing, to produce the conditional probability of the whole set of evidence in existence, assuming the truth of each theory in turn.
  • Finally, we calculate the product of the prior and conditional probabilities of the background and specific evidence, assuming the truth of T, and then assuming the truth of ~T, and then we put these two consequent probabilities into a ratio, giving us the relative probability of theory T.  Since in this case T and ~T exhaust all the possible theories, we can multiply the consequent probability of T by 100 to produce a percentage.

If this does not make sense, please read try the explanations on these pages.

I want to perform a Bayesian analysis on the evidence that convicted Megrahi of the Lockerbie bombing, both out of interest to see the result, and in order to show up clearly which errors of reasoning, if any, the judges fell into.

Now, let's determine the prior probability that the narrative of the crime constructed in the verdict was a true reflection of events, considering only such general background knowledge as we have and was included in the verdict.  An expert in airline logistics and criminology would obviously be able to give more expert opinions, but I will do the best I can according to my own lights.  I will assume that if the bomb was loaded at Malta, then Megrahi was the guilty party.  We can express the relative probabilities of each piece of evidence, background or specific, on each theory T and ~T as a ratio: 1:1 when the evidence is equally probable on either theory; 10:1 if it is 10 times more probable assuming the truth of T than ~T.


Background knowledge leading to a prior probability
  • How probable was it that a bomb could be introduced onto a plane at Luqa airport?
As per the verdict:
The evidence of the responsible officials at the airport, particularly Wilfred Borg, the Air Malta general manager for ground operations at the time, was that it was impossible or highly unlikely that a bag could be introduced undetected at the check-in desks or in the baggage area, or by approaching the loaders, in view of the restricted areas in which the operations proceeded and the presence of Air Malta, Customs and military personnel. Mr Borg conceded that it might not be impossible that a bag could be introduced undetected but said that whether it was probable was another matter. ... the Crown accepted that they could not point to any specific route by which the primary suitcase could have been loaded ... The absence of any explanation of the method by which the primary suitcase might have been placed on board KM180 is a major difficulty for the Crown case... (p. 41-2)
I would normally rate the probability of a bomb in a suitcase getting onto a plane at Luqa airport at lower than 1%, based on the expert evidence that it was "impossible or highly unlikely".  I shall rely on this evidence, even though it could potentially be biased against the possibility by Mr Borg's care to safeguard his reputation.  But, for the sake of making Megrahi's guilt as probable as we can reasonably make it, in order to find the maximum probability that he was guilty, I will go ahead and allow a 10% probability.  This is way higher than the real probability, but if we use maximum probabilities then we will at least know by the final calculation that Megrahi's guilt cannot be any more probable than the number we calculate in the end.

  • How probable was it that a bomb such as destroyed Pan Am 103 could have evaded x-ray detection at Frankfurt?
The bomb was hidden in a Toshiba radio.  Not only were the normal x-ray checks done on the luggage that transferred at Frankfurt onto the plane to Heathrow that was set to go on to New York City, Pan Am 103, but at Frankfurt the x-ray operators were under special warning to watch out for bombs hidden in radios.  The judges were aware of this:
It was submitted that the x-ray would, in all probability, have detected any explosive device in a case, particularly as the staff at Frankfurt were aware of warnings to look out for explosive devices hidden in radio cassette players. One such warning was issued after the Autumn Leaves operation in October 1988. Another, more limited, warning was issued because there was understood to be a threat that a woman from Helsinki would attempt to smuggle a device on board an aircraft. It was submitted that that examination would have revealed the presence of the radio cassette player and its contents, particularly in view of the fact that there had been a warning to look out for explosive devices hidden in radio sets. (p. 37)
 However, with regard to Mr Maier, the relevant x-ray operator, whose written statements were entered as evidence since he was too ill to attend the trial:
Mr Maier explained that he had had some limited training in the use of the machine, but said that in the course of using it he had taught himself to distinguish various sorts of electrical equipment, and that he knew how to tell if explosives were present, from their appearance. Neither statement directly dealt with the question whether, and if so how, Mr Maier would detect explosives hidden in a radio cassette player. What he said was that the approach in dealing with electrical equipment was to see whether it presented a normal appearance, for example whether it had a plug. Other evidence, however, particularly the witness Oliver Koch, Alert’s trainee manager at the time, shows that the standard of training given to Alert employees was poor. That was also the view of the FAA investigators who visited Frankfurt in 1989. Mr Maier’s description of what he looked for does not suggest that he would necessarily have claimed to be able to detect explosives hidden in a radio cassette player. There was no expert evidence as to the ease or difficulty of detecting such hidden devices. The x-ray examination is one of the factors to be taken into account but it is only one factor to be weighed along with the others.  (p. 38)
It is difficult as a non-expert to know the probability of the bomb being detected.  The existence of the warning argues in favour of it, but the low quality of training argues against it.  It is frustrating that such a low standard of evidence was left unimproved due to the illness of a man.  Surely courts should have a means of asking for important evidence that was not presented at trial before reaching a verdict!  Anyway, I will allow an outside 50% chance that the bomb could have got through this dubious security system.

We need to multiply together the probabilities of the bombs being loaded at Luqa and evading detection at Frankfurt.  10% multiplied by 50% gives a 5% outside chance.  So, based on these elements of background knowledge, it was at best highly improbable, 19-to-1 against, that the crime could have been committed as the verdict said.

It was a highly unlikely crime to come off.  That does not mean Megrahi did not beat the odds and commit the crime in this way.  If the specific evidence of his involvement is sufficiently strong, in that it demands decisively to be explained by his guilt as per theory T, then the conditional probability may be high enough to overcome the inherent improbability of the crime.


Specific evidence leading to a conditional probability

Here is the concluding paragraph of the verdict listing the main points of evidence adduced against Megrahi.  I have coloured the separate points that I will deal with so as to bring out how I will deal categorise and consider the evidence:
We are aware that in relation to certain aspects of the case there are a number of uncertainties and qualifications. We are also aware that there is a danger that by selecting parts of the evidence which seem to fit together and ignoring parts which might not fit, it is possible to read into a mass of conflicting evidence a pattern or conclusion which is not really justified. However, having considered the whole evidence in the case, including the uncertainties and qualifications, and the submissions of counsel, we are satisfied that the evidence as to the purchase of clothing in Malta, the presence of that clothing in the primary suitcase, the transmission of an item of baggage from Malta to London, the identification of the first accused (albeit not absolute), his movements under a false name at or around the material time, and the other background circumstances such as his association with Mr Bollier and with members of the JSO or Libyan military who purchased MST-13 timers, does fit together to form a real and convincing pattern. There is nothing in the evidence which leaves us with any reasonable doubt as to the guilt of the first accused, and accordingly we find him guilty of the remaining charge in the Indictment as amended. (p. 82)
I shall take the evidence against Megrahi point by point.  Let us see if they really do "fit together to form a real and convincing pattern".

  •  The bomb-suitcase containing clothes from Gauci's shop in Malta, and Gauci's "identification of the first accused (albeit not absolute)" (there was a second accused who was found no guilty).
I will assume that whoever bought the clothes in Gauci's shop, that later went into the bomb-suitcase, was the guilty party.  Now, the fact is that Mr. Gauci did not really identify Megrahi as the purchaser of the clothes:
Mr Gauci picked out the first accused at an identification parade on 13 August 1999, using the words as written in the parade report “Not exactly the man I saw in the shop. Ten years ago I saw him, but the man who look a little bit like exactly is the number 5”. Number 5 in the parade was the first accused. He also identified him in Court, saying “He is the man on this side. He resembles him a lot”.  (p. 55)
Also:
Mr Gauci’s initial description to DCI Bell would not in a number of respects fit the first accused.  (p. 65)
Gauci actually mischaracterised Megrahi to the police in terms of his age and height.

Let us consider this evidence in Bayesian style.  That means determining the probability that Gauci would say the purchaser of the clothes resembled Megrahi, and tell the police at first that the customer was of the wrong age and height, first assuming Megrahi's guilt, then assuming his innocence.  If Gauci had indeed sold the clothes to Megrahi, I would expect him to pick him out fairly definitively.  If Megrahi was not the man, then I would expect Gauci to say at best that Megrahi only looked "a little bit like exactly" the man and fail to give police an exact description.

What is bizarre is how the judges reasoned about this uncertain semi-identification:
Unlike many witnesses who express confidence in their identification when there is little justification for it, he was always careful to express any reservations he had and gave reasons why he thought that there was a resemblance. There are situations where a careful witness who will not commit himself beyond saying that there is a close resemblance can be regarded as more reliable and convincing in his identification than a witness who maintains that his identification is 100% certain. From his general demeanour and his approach to the difficult problem of identification, we formed the view that when he picked out the first accused at the identification parade and in Court, he was doing so not just because it was comparatively easy to do so but because he genuinely felt that he was correct in picking him out as having a close resemblance to the purchaser, and we did regard him as a careful witness who would not commit himself to an absolutely positive identification when a substantial period had elapsed. We accept of course that he never made what could be described as an absolutely positive identification, but having regard to the lapse of time it would have been surprising if he had been able to do so. (p. 66)
That's right!  The tentativeness of Gauci's identification was taken not as an indicator of its weakness, but explained away as care to be accurate!  This is completely the wrong way to handle uncertain evidence.  Gauci's identification should be held highly suspect because it was so uncertain, not lauded as the best that a careful witness would allow himself to say.

I would rate the probability of Gauci failing to identify Megrahi properly if he were the purchaser of the clothes as 50%.  If Megrahi were not the purchaser, I would rate Gauci's semi-identification of Megrahi as perhaps 90%, given that on this theory Megrahi would merely have the misfortune of somewhat resembling the real purchaser.

So Gauci's semi-identification evidence is actually a blow for the theory of Megrahi's guilt by a ratio of 9:5.  Percentage-wise, the probability of Megrahi's guilt, given Gauci's evidence, would be 5 in 14, thus 36%.

You can start to see what mistake the judges made: they chained together a series of improbabilities as if they added up to a probability.  Rather, they multiply up to a greater improbability!

Note that Kerr in her book totally undermines the validity of Gauci's evidence.  Among other things, Gauci had seen a photograph of Megrahi linking him with the Lockerbie bombing before he ever spoke with the police.  Furthermore, Gauci also told police that a picture of an Egyptian terrorist named Abu Talb resembled the customer, and this suspect is known to have visited Malta before the bombing, giving him the opportunity to buy clothes at Gauci's shop.

  • The transmission of an item of baggage from Malta to Heathrow.
The issue of whether a piece of unaccompanied luggage passed from Malta to Heathrow via Frankfurt is very complicated.  Suffice to say that Kerr shows the system was basically a mess, and the mystery bag supposed to be in the system could just as easily have come from Warsaw as Malta.

An example of how Kerr describes the transfer-baggage mess:
Not only could no bag from Malta be discovered, at least thirteen more items remained unaccounted for. Given the sheer number of untraceable baggage trays there was really no reason to believe any particular one of them was the bomb, and the German police gave up. They appear to have been so thrown by the impenetrability of the worksheets they decided the whole thing was a complete waste of time. ... [The German investigator] doggedly hunted for some legitimate item of luggage that might have been in tray 8849 [supposedly transferred from the flight from Malta]. He failed – but then, he also failed to trace anything that might have been in at least five of the other trays on the printout, which puts that into a bit of perspective.
Kerr quotes from the summary of the German police investigation of the Frankfurt element of the case:
This item of luggage cannot be said with certainty to originate from KM180 [from Malta] for the following reasons. [Many reasons given.]  Throughout the inquiries into the baggage for PA103A there was no evidence that the bomb suitcase had been transferred with the luggage either from or via Frankfurt Main to London.
 She goes on:
The Scottish branch of the Lockerbie investigation, despite having found nothing on Malta to contradict that position, simply ignored him.
 So it is strange to read this from the judges:
The evidence in regard to what happened at Frankfurt Airport, although of crucial importance, is only part of the evidence in the case and has to be considered along with all the other evidence before a conclusion can be reached as to where the primary suitcase originated and how it reached PA103. It can, however, be said at this stage that if the Frankfurt evidence is considered entirely by itself and without reference to any other evidence, none of the points made by the defence seems to us to cast doubt on the inference from the documents and other evidence that an unaccompanied bag from KM180 was transferred to and loaded onto PA103A.  (p. 38)
The judges thought they had good documentary evidence that an unaccompanied bag transferred at Frankfurt from Malta.  They did however consider some issues with the evidence, including the issue about an unaccompanied bag from Warsaw:
Reference was also made to another item in production 1060. ... this bears to show that an item coded at a station in HM at 1544 on 21 December also was sent to PA103A, and reference to the coders’ records bears to show that baggage from flight LH1071 from Warsaw was being encoded at that station at that time. It was agreed that no passenger from that flight transferred to PA103A, so that the records seem to show the presence of another unaccompanied bag on that flight. (p. 36)
After mentioning this issue, however, the judges do not go on to provide any analysis of it.  It is incredible!  They had evidence that the supposed bomb-suitcase could have come equally well from Warsaw as Malta.  Yet they mentioned this evidence only to ignore it completely!

If we include the evidence of a bag transferring from Malta, and say it was 10 times more likely that an unaccompanied bag transferred from Malta via Frankfurt on the hypothesis of guilt than on the hypothesis of innocence, then this would be strong evidence against Megrahi.  So we can also say that the judges' misuse of the baggage evidence, if they were thinking in Bayesian terms, would have been a very significant mark against Megrahi (it would make my final calculation 72%, so positive but not really enough to exclude reasonable doubt).  However, apart from Kerr's demonstration that the evidence did not necessarily mean what the judges thought it meant, the judges seriously misused even the evidence as they saw it.  They completely ignored the evidence that the purportedly unaccompanied bomb-suitcase might have come as easily from Warsaw as Malta.

Let's see what would have happened if the judges had included in a Bayesian calculation the evidence about the Warsaw bag.  This is actually an interesting bit of probability work.  Assume that an unaccompanied bag has a high probability of containing a bomb, as is required by the judges' reasoning about the evidence of the bag that they thought came from Malta.  What then is the probability that an unaccompanied bag would get onto the Frankfurt-Heathrow feeder flight from Warsaw on the hypothesis of Megrahi's guilt?  Call that number x.  It has to be a low number, since this bag cannot be the bomb, yet unaccompanied bags, ex hypothesi, are likely to contain bombs.  It is therefore an improbable sort of bag.  Now, what is the probability of such a bag feeding onto the flight from Warsaw on the hypothesis of Megrahi's innocence?  Surely it is a number much greater than x.  This is because, if an unaccompanied piece of luggage is regarded as likely to contain a bomb, and a bomb was fed onto the Heathrow flight, but that bomb did not come from Malta, then it must have come from Warsaw (or even somewhere else, since there were other dubious transferred bags).  Therefore, assuming unaccompanied bags are likely to be bombs, which the judges must believe, the correct Bayesian interpretation of the existence of a piece of unaccompanied luggage feeding in from Warsaw is that this fact is much more likely on the hypothesis of Megrahi's innocence.  Alternatively, if unaccompanied bags are regarded as not likely to contain bombs, then the evidence that an unaccompanied bag came from Malta is no more probable on the hypothesis of guilt that on innocence.

Since the judges included as a fact the existence of a suitcase from Malta, and might have rated that as, say, 10-to-1 evidence against Megrahi, by the same token they should really have rated the existence of a suitcase from Warsaw, equally likely to have existed, at the same 10-to-1 in Megrahi's favour.  This is because, if the existence of a bag transferring from Malta makes it more likely that the bomb came from Malta, then the existence of a bag transferring from Warsaw does the same for the Warsaw origin.  So the net effect of the evidence the judges had about luggage transferring at Frankfurt should have been neutral: 1:1

Kerr gets much closer to a correct understanding of the importance of the mysterious bag that seems to have come from Warsaw, even though no legitimate transfer baggage was supposed to come from that flight:
Both [the Malta and Warsaw mystery bags] were single items apparently coded at a time and a place where no legitimate luggage for PA103A was being handled. We’re completely out of legitimate luggage to reconcile to either of them. More lost, misrouted or rush-tagged cases being shuttled to Heathrow? Who knows. The fact is, though, that it has happened twice, and in the context of a significant number of other items being less than conclusively reconciled. Tray 8849 is anything but an isolated anomaly shrieking “bomb here!”

  • Megrahi's association with Libyan intelligence and with people who sold and handled the MEBO timers, one of which set off the Lockerbie bomb.
Kerr's investigation shows that this evidence was flawed as well, since the timer was of a type not used by the Libyans (it was made with pure tin rather than alloy, so it does not match the items made for Libya).  But I will disregard this and focus on the judges' reasoning.  Let us accept for sake of argument that Megrahi had access to the timers, one of which set off the bomb.  The judges believed the timer was of a kind only supplied in an order of 20 to the Libyan military.  What follows?

It follows that Megrahi would have had the opportunity to commit the crime.  But it does not follow that it is probable that he did it.  There is a huge difference between possible and probable.  Only if Megrahi's access to the timers makes it probable that he committed the crime should the judges draw a positive conclusion from this piece of evidence.

Let's look at this point in Bayesian style.  What is the probability that Megrahi would turn out to have access to the MEBO timers if he committed the crime?  Obviously 100%.  What is the probability that Megrahi would turn out to have access to the MEBO timers if he did not commit the crime?  Obviously still 100%!  The access and association are certain on either theory because they refer to the time before the crime.  What access and association Megrahi had before the crime is not evidence of whether he not he committed it, except in the sense that they made it possible for him to have committed it.

This was a crucial mathematical error by the judges.  The (purported) fact of Megrahi's access to the right sort of timers only raises the probability that he committed the crime in the sense that it makes it possible rather than impossible.  It does not make it probable, since even if he did not commit the crime, it would still be a fact that he had access to the timers.  Therefore the correct use of this evidence is to regard it as indifferent towards the relative probabilities of theories T and ~T.  It should have no positive effect moving the judges towards a guilty verdict, except in so far as making it possible that Megrahi committed the crime.  There can be no movement above 50% probability however.  The correct ratio to draw from his access to the timers is 1:1.

It is not as if only Megrahi had access to these specific timers, and it is not as if the Libyans could not have sold or supplied them to somebody else.  The CIA had an equivalent that they had seized in Togo, so who knows what hands the Lockerbie one might have been through?  It is even possible that the Libyan timers were used by Libyans to carry out the bombing, but not by loading the bomb at Malta.  Warsaw, as we saw, was an equally probable origin as per the evidence the judges considered; and in fact Heathrow was a far more likely origin, as I explained in my previous post.

However, we can also ask how probable it was that the bombing would be perpetrated using these specific MEBO timers on the hypothesis that Megrahi did it (on orders from Libyan military or intelligence forces), compared with the probability on the hypothesis that he did not.  It can be argued to be more likely that such timers would be used if Megrahi committed the crime than another, non-Libyan culprit.  But since we could not say that the timers were not used by another Libyan in Warsaw or Heathrow, or supplied to other forces by the Libyans, I am not prepared to grant a significant imbalance in the probability in favour of Megrahi's guilt.  There are lots of other possibilities that also involve the use of the same timer.

Furthermore, Kerr explains another alternative possibility:
The Blinkbonny fragment almost certainly originates from the same template as the Thüring boards [those supplied by MEBO]. That doesn’t, however, mean that it must have been made directly from that template. Printed circuit boards are easy to copy by photographing them, and any such second-generation copy would reproduce the tracking irregularities from the original. Anyone who had an original timer or even just a circuit board could make such a copy. ... had some other group who had got hold of one of the original models decided to copy this nifty little number for themselves?
So the timer would not even necessarily be one supplied to Libya by MEBO; it could be a copy.

As I noted, Kerr's analysis makes this discussion of the timer academic, since she shows that it was not the same as that supplied to Libya after all.  The timer's provenance is in fact rather mysterious.

  • Megrahi's presence in Malta on a false passport at or around the material time.
Megrahi failed to provide an explanation for this.  Were the judges right to draw an adverse inference from this?  Let's consider: would Megrahi be more likely to fail to do so if were guilty of the crime, than if he were innocent?  It is probably fair to say that, were he in Malta on an innocent mission for the intelligence services, he would have explained this to the court to try to save himself from prison.  On the other hand, there may be other reasons why he felt he could not reveal why he was there.  I don't know.  It looks bad for Megrahi, I will say by 10-to-1.

Let's calculate the conditional probability of Megrahi's guilt, based on the specific evidence the judges relied on.  The ratio of probability on T relative to ~T is 5:9 times 1:1 times 1:1 times 10:1 equals 50:9, or an 85% conditional probability of guilt.  As can be easily seen, the only evidence that supports Megrahi's guilt is his failure to explain his presence in Malta on a false passport.  The identification evidence is so weak as to work in favour of his innocence, the evidence of a transfer bag from Warsaw neutralises the evidence of a bag from Malta, and the timer evidence is indifferent between guilt and innocence.  Megrahi should certainly have come up with a reason for his suspicious activity.


Consequent probability

In order to find the probability of guilt that the judges should have arrived at by applying correct, Bayesian reasoning to the evidence they cited, we plug our numbers into the formula using Richard Carrier's online Bayesian calculator:


That is, the highest probability of guilt that the judges should have arrived at was 23%.

To explain the arithmetic, the prior probability of guilt (5%) is multiplied by the conditional probability of the specific evidence on the hypothesis of guilt (85%).  The product is divided by the sum of the product of the prior probability (5%) and the conditional probability of guilt (85%) and the product of the prior probability of innocence (95%) and the conditional probability of the specific evidence on the hypothesis of innocence (15%):

(0.05 x 0.85) / (0.05 x 0.85)+(0.95 x 0.15) = 0.0475 / 0.185 = 23%.

Megrahi should have been found not-guilty (or alternatively not-proven in the Scottish legal system).  This result is based on the evidence the judges had, except for the misused evidence about the baggage transfer which I excluded because its use contradicted the findings of the police report.

The crime was such an unlikely one that terrifically good specific evidence was needed just to make Megrahi's guilt turn out probable.  If the conditional probabilities were 99:1 for Megrahi's guilt, then the consequent probability would turn out as 84%.

The judges' crucial error is clear and highly important as an example of how forensic and historical reasoning can go badly wrong:

They chained together a series of improbabilities as if they added up to a probability.  Rather, they multiply up to a greater improbability!

The crime was hugely improbable on background knowledge alone.  The identification evidence was so poor as to work in favour of acquittal, whereas the judges used it to help establish guilt.  The evidence of Megrahi's access to the timer used was irrelevant, but the judges used it to help establish guilt.  Of all the evidence, only Megrahi's failure to explain his suspicious behaviour was a real piece of evidence against him.


Conclusion


The judges failed to use Bayesian reasoning, which would have shown them that, far from a series of improbabilities adding up to a proof of Megrahi's guilt, they should have multiplied them out to a much greater sense of doubt.  They failed to appreciate that the crime was such an unlikely one on principle, that iron-clad evidence of Megrahi's guilt was required to overcome the prior improbability: extraordinary claims require extraordinary evidence.  A circumstantial case built on improbabilities does not cut it.

If the judges had applied correct probabilistic reasoning to the facts they did have about an unaccompanied bag from Warsaw, then this would have neutralised the evidence of an unaccompanied bag coming from Malta.

Of course, if we included the evidence explained yesterday, and considered how probable it was, on a hypothesis of Megrahi's guilt, that a mysterious suitcase answering to the description of the bomb-case would be seen by a baggage-handler at Heathrow before the feeder flight from Frankfurt had even arrived, then it would only be fair to divide the 23% we have come to here by maybe 10 times, if not more.  Include all the evidence, and the probability of guilt is minimal.

Moreover, include a more realistic expectation of the probability of getting the bomb into the baggage system at Malta, and the probability drops again to a miniscule number.

In sum, even without the new understanding born of Kerr's investigation, Megrahi should not have been found guilty.  With it, his innocence is proven.

Thus the worst mass-murder in British history, the killing of 270 people, should be regarded as an unsolved crime.

Thank you for reading if you got all this way!

Friday, 15 August 2014

Why the Lockerbie bomb was loaded at Heathrow and Megrahi was innocent

It is slightly shocking that Morag Kerr's book, which gives the first ever convincing, evidence-based reconstruction of the Lockerbie bombing, has not been reviewed in a major UK-wide newspaper since coming out in December.

[Edit: I'm honoured that my posts on Lockerbie have been linked to by Robert Black, QC, who has been working to get to the bottom of this case for a long time.  I'm also honoured that Morag Kerr has discussed her thoughts with me in the comments sections of both my posts.]

She completely rebuts the case which was pressed by the Crown and accepted by the Camp Zeist court against the late Abdelbaset al-Megrahi, a Libyan agent, who served eight years in prison in Scotland after conviction.  She also shows how the crime was really committed: not by Megrahi loading the suitcase with the bomb at Malta, to be transferred at Frankfurt onto the plane to Heathrow that was set to go on to New York City, before detonating over Scotland, but rather by persons unknown spiriting the suitcase onto the plane at Heathrow by placing it in a luggage shed ready to go directly on board Pan Am 103 to New York City.

Here I want to briefly explain why Kerr is right that this was how it was done.  (In the second part of this analysis of the Lockerbie bombing, I perform a Bayesian probability analysis of the evidence used to convict Megrahi.)

The original guilty verdict against Megrahi argued that he must have infiltrated the bomb past security and onto a plane at Luqa airport in Malta in order to feed via Frankfurt and Heathrow onto Pan Am 103 to New York City.  The judges had to accept that the Crown had presented no evidence as to how he might possibly have done this, given the tight security at Luqa:
If therefore the unaccompanied bag was launched from Luqa, the method by which that was done is not established, and the Crown accepted that they could not point to any specific route by which the primary suitcase could have been loaded ... The absence of any explanation of the method by which the primary suitcase might have been placed on board KM180 is a major difficulty for the Crown case, and one which has to be considered along with the rest of the circumstantial evidence in the case. (p. 42)
The judges thought the Crown had assembled a cogent circumstantial case pointing to Megrahi's guilt, but it is remarkable that they convicted him of a crime it was apparently unfeasible to commit.  Kerr's analysis shows the fallacies and misconstruals of evidence in the circumstantial case, but let's focus on Heathrow.

The evidence of how the bomb was in fact loaded at Heathrow, only recently properly explained by Kerr, was known to the judges.  Unfortunately, they dismissed it with fallacious reasoning and so condemned an innocent man to prison.  I will stick to the essentials of the evidence here.

On the day of the bombing, one John Bedford was working in the air-side luggage area at Heathrow.  He prepared some luggage containers like those in the picture for Pan Am 103, filling them with luggage that was sitting in the shed where he was working.


Bedford went for a tea-break during the afternoon, leaving a partially full container to fill when he returned to work.  On his return, he found two suitcases had been loaded into the bottom of the container, both lying flat in front of the row of upright cases he had previously loaded along the back.  The one on the left he later described to police as a “a brown hardshell, the kind Samsonite make.”  That is in fact exactly the kind of suitcase that contained the bomb, and Bedford described it thus before the police even knew such a suitcase contained the bomb (the investigation involved painstaking reconstruction of the bomb-suitcase from scattered, charred wreckage).  The cases had the right security stickers on them.  Bedford says his colleague told him he had x-rayed the cases and loaded them into the container, which said colleague, one Mr Kamboj, denied.  Anyway, the case Kerr identifies as the bomb-case was in the luggage container.  The feeder flight from Frankfurt had not yet arrived.

How might this suitcase, if it were the bomb-case, have evaded Heathrow security?  There had been a break-in the night before so that is a plausible route.

This would seem a much more plausible way for the bomb to have got on board the plane than the judges' unfeasible Malta method.  Moreover:
It was argued on behalf of the accused that the suitcase described by Mr Bedford could well have been the primary suitcase, particularly as the evidence did not disclose that any fragments of a hard-shell Samsonite-type suitcase had been recovered, apart from those of the primary suitcase itself. (p. 27)
So the judges knew there was no evidence of a second hard-shell Samsonite being present other than the bomb-case, so if Bedford was right about the description of that case, then it was almost certainly the bomb-case.  (Is it not amazing that a man was convicted and sent to prison for over 20 years on the basis of the unmotivated dismissal of such evidence in his favour?)

How then did the judges dismiss the value of the evidence of Bedford and his colleagues?  The verdict argued that, since the site of the bomb-blast was next to one side of the container a little way up, and not against the flat bottom, and the suitcase Bedford saw was lying on the bottom of the container, that case could not have been the one containing the bomb.  That was the most crucial mistake that Kerr detected, of which more shortly.

The judges considered whether the Bedford case might have been moved into the "right" position.  Read what the verdict said on this point:
It was accepted, for the purposes of this argument, that the effect of forensic evidence was that the suitcase [containing the bomb] could not have been directly in contact with the floor of the container. It was submitted that there was evidence that an American Tourister suitcase, which had travelled from Frankfurt, fragments of which had been recovered, had been very intimately involved in the explosion and could have been placed under the suitcase spoken to by Mr Bedford. That would have required rearrangement of the items in the container, but such rearrangement could easily have occurred when the baggage from Frankfurt was being put into the container on the tarmac at Heathrow. It is true that such a rearrangement could have occurred, but if there was such a rearrangement, the suitcase described by Mr Bedford might have been placed at some more remote corner of the container, and while the forensic evidence dealt with all the items recovered which showed direct explosive damage, twenty-five in total, there were many other items of baggage found which were not dealt with in detail in the evidence in the case. (ibid.)
To summarise the argument, the judges said that in order for the Bedford case to be the bomb-case, it would have had to be moved, and that while this may have occurred, it might not have been moved into the "right" position, and it may thus have been among the other scattered suitcases not directly scorched by the blast.  This would presumably require Bedford to have mis-described the case, assuming that it were not known to be among the other pieces of luggage.  It is absurd to imagine that the case as described by Bedford was known to be among the other luggage, and yet such a fact would not be checked and presented by the police and the Crown.  So Bedford must have arbitrarily mis-described the case he saw so as to perfectly fit the actual bomb-case.  Is this a rational conclusion for the judges to draw?  It was also perfectly plausible that the Bedford case had been moved into the "right" place, and does this not produce a reasonable doubt that this was how the crime was committed?

Anyway, Kerr shows that the crucial mistake made by the experts and judges was a different one (Kerr relies on the work of the defence's Northern Irish forensic experts here, but she seems to be the first to realise its importance and to put the whole case together in the convincing way she has done).  The mistake was to think that Bedford's case, even though it were left lying on the bottom layer of cases in the front of the container, could not have contained the bomb that exploded a little way up the side of the container.

The luggage container was of this type:


The bomb-blast was expertly determined to have happened here, raised 10 inches off the bottom in the irregularly shaped part of the container, and towards the front:


As the judges accepted and according to the expert, if the blast occurred there, then Bedford's case, lying flat on the square bottom of the container, could not have contained the bomb.  Rather, they thought the bomb-case must have been placed in one of these two ways:

However, as Kerr shows, they neglected a third possibility:

That is, with the Bedford bag lying indeed on the bottom layer at the front, but not fitting on the square bottom.  Rather, raised onto the irregular, diagonal side, lying on a slight slope, and thus lifting its cross-section into position to contain the bomb-blast.  This fits with the forensic experts saying the bomb-blast was not detonated against the square bottom of the container.

Kerr explains:
[Defence experts] didn’t appear to have any serious problem with the idea that the bomb suitcase might have been the one on the bottom of the stack. They noted that the cases aren’t necessarily regularly stacked in the containers, like bricks in a wall; the loading can be a bit haphazard, as the photograph [above] demonstrates. The photograph is of a similar container loaded randomly for a test explosion, shown in a BBC2 Newsnight feature on 6th January 2010. It wasn’t packed with the intention of illustrating this point. ... Whether the left-hand suitcase was flat or partly in the overhang when Bedford saw it was yet another question nobody thought of asking.
Kerr goes on to show that the blast forensics in general was highly questionable, and argues that her scenario fits with the photographic evidence of the wreckage.  She writes:
It is absolutely clear that the blanket assertion in court from AAIB and RARDE investigators that the bomb suitcase could not possibly have been on the bottom layer of the stacked luggage was not well-founded. It was based solely on examination of the container itself, and appears to consist of little more than unsupported opinion.
The forensic scientists from Northern Ireland didn’t regard the condition of the container floor as an insuperable barrier to the bomb suitcase having been on the bottom layer. Other independent forensic experts agree, adding the opinion that Feraday’s estimate of 25 to 28 cm (10 to 11 inches) for the height of the explosion is too high, with the pattern of damage to the horizontal strut suggesting 7 to 9 inches (17.5 to 22.5 cm). Even 25 to 28 cm would only allow for a fairly thin suitcase to have been under the bomb – something significantly thinner than Tricia Coyle’s large case. A height of around 20 cm (8 inches) is a slam-dunk for the bottom layer, and position 3.
 You will have to read the book and judge the forensic complexities for yourself.  For my part, I am convinced that Kerr is the first person to accurately reconstruct the Lockerbie bombing.  It was a crime perpetrated at Heathrow, and an innocent man suffered for it.  It is a textbook case of a miscarriage of justice, featuring leads missed by the police, unfeasible reconstructions of events and incompetent experts, as well as misconstrued, unreliable evidence both material and eye-witness.  The judges constructed a circumstantial case by irrationally explaining away key exculpatory evidence.  Kerr's book is not only a triumph of critical, evidence-based investigation, but also an instructive example of how a miscarriage of justice can occur.

Thursday, 14 August 2014

Resources for reality-based discussion of Israel/Palestine

I want to use this page to record links to important information about the Israeli-Palestinian conflict that is useful for busting myths put about by either side.


Firstly, this book by Michael Palumbo is in my opinion a well supported critical analysis of Israel's role in the Nakba.  It uses a lot of neutral sources, especially foreign and UN observers.  Although I don't think he can establish his case that the Israeli authorities had a deliberate prior masterplan to expel the Palestinians from a wide area of the country, he does establish clearly what Israeli forces did, where and when to force Palestinians out.  The main virtue of the book is its disproof of the myth that the Palestinians were not expelled from Israel in 1947-8.  It can be found second-hand online.  His critique of Benny Morris and the Israeli revisionist school in general is here.


The second is background rather than news, a myth about the Palestinians that is more stubborn than all the rest: that Arafat rejected a wonderful Israeli peace offer at Camp David in 2000. This was a version of events put about by Denis Ross and Bill Clinton, and repeated by people who don't realise that several other witnesses to those talks give a different view...

Robert Malley, special assistant to Clinton: "it fails to capture why what so many viewed as a generous Israeli offer, the Palestinians viewed as neither generous, nor Israeli, nor, indeed, as an offer."  Or in the words of Aaron David Miller, Ross' assistant: "There was not a formalized, written proposal that covered the four core issues. There was no deal on the table. None of the issues were explained enough in detail to make an agreement..."   And anyone who wants to take the time to understand the Pal point of view can read this account by a member of their negotiating team.  Lastly, here is how Gush Shalom visualised what Barak was suggesting.  So, please, no more of this myth from anybody who hasn't taken the time to consider different points of view provided by a variety of witnesses.

There have also been two exposés of the failure of recent (2014) Israel-PA negotiations.


Thirdly, regarding the fighting in Gaza in 2014, the scale of misinformation over Israel and Gaza was mind-boggling. Firstly, the original kidnapping was apparently carried out by a rogue Hamas affiliate, not Hamas HQ.  [Edit: a Hamas leader later made a claim of responsibility in the name of the organisation.]  Secondly, the Israeli government apparently knew the boys had been quickly killed, but gagged the media from revealing this and took the crisis as an opportunity to "mow the grass" as it were in the West Bank.  Thirdly, the government apparently lied about tunnels infiltrating into kibbutzim to target kindergartens and other civilian areas.  It was also problematic for critics of Israel that while they debunked many such claims from the government during the fighting, they had nothing to say about the real existence of Hamas' tunnels, and thus failed to shift the government's best argument for justifying its military actions.


Fourthly, a lot of Liberal Zionists seem to operate with an out-of-date concept of what Israeli society and politics are like.  People need to realise that Israel today is not the Israel of the mid-'90s, where relatively tolerant, liberal people led the culture. Years of both trauma and incitement, and the ballooning of the extreme right wing, have transformed public culture so that hatred, racism and vengeance against Palestinians are rife, and humane, peace-loving people are hounded as traitorous "leftists". A selection of relevant examples: http://tiny.cc/rlo8ix http://tiny.cc/cno8ix http://tiny.cc/1po8ix http://tiny.cc/cro8ix Please note, it is Jewish Israelis themselves who describe their country so - I will put one or two examples below - but for an unvarnished look at the Israeli right wing, this book is essential.

A couple of those examples:
But make no mistake: the gangs of Jewish ruffians man-hunting for Arabs are no aberration. Theirs was not a one-time outpouring of uncontrollable rage following the discovery of the bodies of the three kidnapped students. Their inflamed hatred does not exist in a vacuum: it is an ongoing presence, growing by the day, encompassing ever larger segments of Israeli society, nurtured in a public environment of resentment, insularity and victimhood, fostered and fed by politicians and pundits - some cynical, some sincere - who have grown weary of democracy and its foibles and who long for an Israel, not to put too fine a point on it, of one state, one nation and, somewhere down the line, one leader.
All the seeds of the incitement of the past few years, all the nationalistic, racist legislation and the incendiary propaganda, the scare campaigns and the subversion of democracy by the right-wing camp – all these have borne fruit, and that fruit is rank and rotten. The nationalist right has now sunk to a new level, with almost the whole country following in its wake. The word “fascism,” which I try to use as little as possible, finally has its deserved place in the Israeli political discourse.

Fifthly, more comment than fact, I want to add my voice to calls for a non-violent protest strategy for the Palestinians.  Far be it from me to lecture Palestinians on how to respond to oppression. But I agree with Mustafa Barghouti, Mubarak Awad, and others, that non-violent resistance is the only game in town. There is Palestinian non-violent resistance going on all the time, but, so long as there is a terrorist threat, Israel is able to continue tear-gassing and shooting down protesters with impunity. The real threat of terrorism covers a multitude of Israeli sins. But imagine if the militants gave up their weapons, and thousands of unarmed Palestinians converged on the Wall, on East Jerusalem, into the settlements, onto their stolen olive-groves... even AIPAC could not contain the outrage that would result from the IDF using violence against resolutely non-violent mass protests - if there were only no terrorist threat to dilute and distract from the raw reality of Israeli occupation and oppression. (As if to confirm the Israeli response to non-violent protest, Mustafa Barghouti's resolutely non-violent PNI had its offices sacked during Operation Brother's Keeper.)

There is a case to be made that the best the Palestinians have ever done at invoking international support was at the time of the First Intifada, and that this uprising was perceived abroad (if not by the Israeli public and despite stone-throwing) as an overwhelmingly non-violent one: only 14 Israeli soldiers were killed in occupied territory, 1987-91, and Uri Avnery of Gush Shalom wrote, two years in: "Practically no weapons have been used against the occupation army. No one doubts that secret arsenals of guns exist in the occupied territories - they are, in fact, used to execute informers - yet the decision not to use them against the occupation soldiers has been generally obeyed. This is all the more remarkable, and perhaps even unique, if one considers that thousands of close relatives of people killed, maimed and imprisoned are seething with rage."  That quotation and much more in this book.

I don't know if a fully non-violent national campaign would succeed in moving US policy towards pressurising Israel in the event that the Israeli government continued to deny a state to a non-violent Palestinian people.  There is some historical warrant for hoping so in the criticism and pressure directed towards the Israeli government by the Bush senior administration.  However Bush blamed the Israel lobby for his failure to win re-election, which illustrates its power to control US policy.  Its influence over Congress is especially strong.  I don't know if non-violence would achieve sufficient public and political pressure in the US to push Israel into conceding a viable Palestinian state; I don't know if it would be a largely sufficient factor.  But I do think it is a necessary one.  I just can't see a Palestinian state emerging while Hamas is militarised: the Israeli government will certainly never allow a state that is not demilitarised, inhabited by militants who are not defanged and conciliatory; and the US government will never go very far to pressure the Israelis if they under any sort of threat.


I am a little unusual, I think, in that I am both highly critical of Israel's regime of oppression of the Palestinians, and scathingly critical of Hamas for its criminal, quixotic and counter-productive strategy of armed, largely terroristic struggle.  The Palestinians would be able to struggle much more effectively for a state and a just settlement of the right of return (e.g. compensation) if the Hamas extremists did not futilely strive to destroy Israel.  Unlike most critics of Israel, I think Hamas bears the largest part of the blame for the failure of the Palestinians to gain something close to an independent state since the Oslo Accords.  I'm not sure that most people critical of Israel today realise that Hamas embarked on suicide-bombing campaigns in the 1990s precisely to destroy the peace process.  As Amira Hass, the Israeli journalist, who was living in Gaza at the time explained it: "[suicide bombing] had a clear political motive on the part of Hamas, and this was to foil the Oslo agreements, or to push to a corner the Palestinian Authority. This is, I think, is obvious."  It can be debated whether Hamas opposed the peace process out of refusal of two states in principle, or else more narrowly because they regarded this particular peace process as a "security arrangement" and continuation of occupation in a new form through the Palestinian Authority rather than a genuine peace process.  Leaders made statements of both kinds and I suspect Hamas was divided and ambiguous on this issue then as now.

I am not so naive as to imagine Hamas would ever declare decisively for non-violence.  And when a necessary condition for a realistic peace is impossible, the issue becomes academic, and only a despairing expectation of more of the same spasmodic violence and death is left.