The Binnie Report is Fundamentally Flawed

Firstly, I am not a legal expert, my strengths are science and mathematics and in everything I do, I place immense importance on empirical evidence, in the full knowledge that we can never be absolutely certain about anything and must always proceed on a balance of probabilities.

Justice Binnie was asked to make a balance of probabilities test on a great number of evidential items that incriminate either David or Robin Bain in the murder of their family members. This is the kind of investigation that is better suited to a scientist / mathematician than to a legal mind because it involves largely factual material and a realistic calculation of probability. Legal judgments of probability use a Bayesian calculator as a basis, which is a mathematical tool. While Binnie doesn't convert his probability judgments into numbers to put through this calculator, in the Bain case, due to the rather large number of evidential items and the need for transparency, this could be an advisable course of action.

When doing this we set out a probability against each item of compelling evidence that we can identify was put forward in either trial and in pre-trial events. In so doing, instead of using words such as “likely”, “unlikely”, “speculative”, “credible” etc., we use a number. For instance we could assign probabilities per evidence item as follows:


Probability incriminating Robin

Probability incriminating David

Footprints on carpet



Glasses on David's chair and in Stephen's room



Fingerprints on murder weapon



Bloodied gloves in Stephen's room



And so on...



In the above table each probability is a subjective judgment that gives weight to the argument that the person is responsible for creating either whole or part of the crime as a result of their link to that particular item. The probabilities given in the example above are a guide only.

Binnie’s biggest mistake is to assign more or less 100% probability that the footprints were made by Robin. This is incorrect. While we can assign a probability of 100% to the notion that the footprints were made by the killer, because all parties agree with that, there is too much expert dispute over who might have made them to allow anything like that level of probability here. For the sake of Binnie's argument that the footprints are too small to be David's, even though we don't know whether or not they represent a full footprint, the maximum probability of culpability we might allow is 75% Robin to 25% David, as shown.

The glasses evidence, which involved a lens found on the floor of Stephen's room and the remainder of the glasses on a chair in David's room, cannot simply be ignored, as Binnie has done. This was a most contentious item of evidence during the course of two trials and one civil defamation case. The evidence suggests that the glasses were broken in the fight that occurred between the murderer and Stephen. Just because an item of evidence is contentious, does not make it invalid and in a probability test of this sort it cannot be simply relegated to “unexplained” which is what Binnie has done. It has to be explained, because the onus is on David, and it has to be represented in the probability equation. We know that David used to wear this particular set of glasses when his own were not available and at the time of the murders his glasses were at the optometrist being fixed. Here we have assigned 75% probability that David committed the murders based on this item of evidence. Robin, on the other hand, had no use for them but because the Defence postulated that he might have put them there to incriminate David, which is extremely unlikely, we will allow 1%, which leaves a probability of 24% that the glasses evidence is incidental and nothing to do with the crime.

David's fingerprints were found on the forestock of the rifle. There may have been arguments put forward that blunted the original Crown contention that the fingerprints were in human blood, but simple fact is that only David's fingerprints were found on the rifle and no fingerprints of Robin. Yet Robin would have had to hold the rifle in an awkward position in order to kill himself, if he was to have committed suicide. It is possible that Robin could have wiped all the fingerprints, and then not left any in his final act, so in this analysis we can assign him 25% probability, but we give the balance to David. While clever arguments have been made to explain the origin of the fingerprints, they cannot be taken as fact. They may work in the court room, but based on the known facts about this item it is more likely that David committed the murders than Robin.

David's opera gloves were found bloodied and lying on the floor in Stephen's room which is also consistent with the violent struggle Stephen had with his murderer. It is 100% probable that these gloves were used in the murder but we assign 75% probability that David was wearing them because they are his gloves, and 25% probability to Robin because he had his own set of opera gloves in the caravan and had no need to use David's.

We apply the same process to all the other evidence that incriminates David, such as the presence of Stephen’s blood on the crotch of his pants, and testimony of using the paper run as an alibi, of threatening the family with his gun and the items that incriminate Robin, such as testimony of being depressed, alleged incest and others. Each subjective judgment we make is based on the expert testimony, ie the empirical evidence and the witness testimony of both sides of the argument. We cannot choose whether one set of experts is somehow right and another set wrong unless there is robust cause such as the demonstration of something with very high probability like a DNA match. Other legal opinions can be used, not as evidence, but to help us moderate our assessment and come to a reasonable level of probability.

Once we have gone through each of the items of evidence and assigned probabilities for each of David and Robin, then we might apply a weight to each item, on the basis that some items are more compelling than others. We can then feed the numbers into a calculator such as the Bayesian equation and get an overall probability for each of Robin and David. The beauty of doing it this way, is that if we peer review, then items of probability can be altered and, provided that we use a spreadsheet, our accumulated probability recalculates immediately. In this manner we can respond to disputes over probabilities of individual items very quickly and if necessary add new items or sub-items. Provided that the judgments made at the level of individual items is sound, then we can know that the mathematical calculator provides a reasonably objective means of obtaining the overall balance of probabilities.

All the compelling evidence presented in the various trials from both sides needs to be included in the probability calculation. Because this trial has such a long history there is plenty of testimony and judicial opinion from which to draw. An item cannot simply be cast aside and ignored, which is what Binnie has done repeatedly. The onus is on David to prove innocence which means that where there is doubt, then the Crown argument tends to prevail.

It is clear that Justice Binnie did not do as requested by the Minister of Justice. It appears that he has not based his judgment on factual innocence on the balance of probabilities. I suspect, based on Binnie's focus on allegations of errors by police and injustices by the justice system that his judgment is slewed towards social justice instead. The Minister of Justice has rightfully rejected his report.

  • Joe Karam: They had to base their judgment on the evidence, not their feelings or emotions

    I feel a great pity for the jurors who sat to pronounce verdict on David Bain. I am sure that they were perplexed as to why this perfectly normal young man committed this atrocity. They had to base their judgment on the evidence presented to them, not their feelings or emotions. And the evidence was palpably false and misleading.

    Joe Karam David and Goliath page 137