The governments and judiciaries of English-speaking countries, especially Britain and the United States, frequently proclaim that one of their fundamental beliefs is the rule of law, with the implication that other countries, although possessing legal systems, are not quite as devoted to this notion as they are themselves. One of the most frequently invoked facts in support of this claim is the use of juries in many trials in Britain and the USA. The unquestioned assumption is that thai by jury is superior to trial by a judge or panel of judges. Yet last month the Home Secretary, Jack Straw, announced that the Government wished to abolish the right of a defendant to choose a trial by jury for relatively minor offences. The Government hopes this would result in a higher rate of convictions as well as a saving of £100 million. However, Mr Straw's proposals have roused fury among civil liberty groups and especially among the ethnic minorities.

Is trial by jury superior to any other kind? In other words, is it more likely to allow the truth to emerge and justice be done? Before answering this question, let us consider the traditional arguments for and against juries.

In favour of juries it is held that twelve heads are better than one and that the collective intellectual and moral power of a jury is more than the sum of the abilities of its individual members. It is also claimed that the jury system is less amenable to corrupt influences, it being much harder to bribe twelve people than one judge. Also, the jury allows a certain flexibility in the interpretation of the law, juries being more likely to be more concerned with the spirit, than with the letter, of the law.

Against these advantages is set the assertion that jury members are, in general, less able people than judges and lawyers. They usually have little knowledge of the law and, unlike legally trained people, they are not accustomed to evaluate evidence objectively and to arrive at unbiased conclusions on the basis of it. Moreover, difficult evidence, such as some scientific evidence, is sometimes deemed inadmissible in court, simply because it is felt that the jury would not understand it.

Two other points about juries have been used to argue both in favour of their use and against it. The first point is that people selected to sit on juries are usually inexperienced in life as a whole. Lawyers and doctors are excused jury service. In practice, most professional people, like scientists, are also excused, because they can almost always claim that absence from their duties would cause difficulties for others. The result is that most juries are made up of people who are not used to tackling important problems on a day-to-day basis.

However, it has been argued that inexperience is not necessarily a bad thing, on the basis of what may be called the 'from-the-mouths-of-babes' principle. Inexperienced people may often 'see' the truth more clearly and more readily than people whose minds may be cluttered with laws, rules and conventional ways of doing things. The second point is that justice in a jury system is not, in fact, the rule of law, but the rule of men. A judge would arrive at a verdict on the basis of the strict interpretation of the law (or so it is believed), but ordinary men and women would be more likely to be swayed by pity for the victim or the accused, by their physical appearance (especially if it is a woman), by racial, religious or political prejudice, by local bigotry and so forth. The behaviour of the jury in the criminal trial of O. J. Simpson is a case in point.

Against this, some people have argued that juries can be seen to be the rule of men, not of the law, only in a very superficial sense, since juries are part of the legal system and can be a safeguard against any possible excesses that might happen, if the law was applied without the humane and civilised forces of pity and compassion. This is very similar to the earlier point about adherence to the spirit, rather than the letter, of the law.

What, then, is the answer - are juries good or bad things? As with so many systems devised by man, there is no simple answer. My own experience with the courts leads me to believe that the jury system is not as desirable as it is claimed to be. Legally, it is not permissible to ask a jury member how he arrived at his verdict. Therefore, one cannot know how these decisions are being made. It seems to me that this is an inherent weakness and one which is hardly ever pointed out. Not knowing how a public decision is arrived at cannot be a good thing, especially since we know that juries can hardly fail to include people who are prejudiced, ignorant and stupid, even if this is not the norm. The question is not whether juries include such people, but how often they do. Clearly, it is not possible to answer this question.

The very mystery over this matter seems to me to be an argument against juries. Another argument against them is the fact that, contrary to general belief, they are not provided with all the relevant evidence upon which to base their verdicts. I say relevant evidence advisedly, since it is often stated that judges allow juries to see all such evidence. In my experience, this is not always the case. I have known cases in which the judge withheld from the jury what I considered to be evidence that was highly relevant and I am not referring to such difficult matters as previous convictions. Certain evidence, deemed to be offensive to the sensibilities of juries, is withheld. In one case from my experience, the judge withheld the photographs of the murder scene on the grounds that they were too unpleasant, although they would have helped the jury members to understand the significance of the scientific evidence much more clearly. Thus, it is not true to say that juries see the whole picture; in fact, they see only what they are allowed to see. Judges are often motivated by the best of intentions when they withhold evidence, but the practice in general does not strike me as being helpful.

Information is withheld from juries in more subtle ways than simply being denied access to it by the judge. The nature of the adversarial system can often make this happen in a way that I believe has not been commented upon previously; it is caused by the concept of the 'hostile witness'.

A hostile witness is a witness brought by one side, either Prosecution or Defence, but who gives evidence that weakens or goes against the case of the side that asked him to give evidence. For example, if I am asked by the Prosecution to give evidence, but, while I am in the witness box, I say things that weaken the Prosecution's case, I would be deemed to be a hostile witness. It is generally accepted that one ought not to behave in this manner.

I have never understood this attitude, not only because it is clearly dishonest, but because it must also be legally questionable. If the barrister asks one a question the answer to which is likely to damage his case, what should one do? It seems clear that one must answer truthfully, regardless of whether it supports his case or not. However, this is considered by barristers to be terribly bad form. I have known very able and honest forensic witnesses who have urged the barristers for whose side they were appearing not to ask them certain questions, because the answers would harm their case. Astonishingly, such people sincerely believe that this is the correct way to behave and, indeed, consider themselves to be conducting themselves in a fair and honourable manner when they do this, so strong are the persuasive powers of barristers.

I have said that this practice must be legally questionable and the reason is this. A witness is required, usually under oath, to speak 'the truth, the whole truth and nothing but the truth'. How can this requirement be reconciled with the idea of supporting one's 'side' come what may? Clearly, it cannot, but it is one way by which relevant evidence can be withheld from juries.

On the whole, it seems to me that trial by jury, while having many theoretical advantages, does not live up to its exalted reputation, partly because of the fundamental weakness of a system that appoints people of unknown intellectual and moral calibre and partly because of the way it is manipulated (whether such manipulation be benign or malign), by lawyers and judges. It is certainly my strong impression that lawyers, judges and police officers usually have little regard for juries.

An incident from my experience revealed to me the real attitude that some judges have towards juries. It was a case of murder. Some time before the trial began, I was interviewed by a newspaper reporter about my views on the state of forensic science in Britain. I expressed my opinion that many forensic practitioners were incompetent or corrupt, but, of course, I mentioned no specific individuals or cases. The interview was concerned with general principles and was of a kind I had given on previous occasions. The article was published in the newspaper on the day before I was due to give evidence at the trial. I should mention that I had no idea when the article was going to published, nor did I know when I was due to be called to give evidence.

When I arrived at court, I was informed that a little problem had arisen and was asked to wait in the corridor. To cut a long story short, the judge, under pressure from the Defence barrister, decided to abort the trial and postpone it for six months, since the article was deemed to have prejudiced the jury. The Defence barrister claimed that those jury members who might have read the article would be disposed to believe me, rather than the Defence consultant.

In order to try and extract some kind of explanation for what happened, I decided to write to the judge. The following is an extract from the very long letter I sent him: 'The article is not evidence in this trial. The court, however, felt that it might prejudice the jury. Is this to be taken as an indication that the court does not believe that the jury has the ability to distinguish between what is evidence and what is not?'

Aborting the trial suggested that the court did not believe that the jury could be relied upon to make the distinction, yet these were the very people who were appointed to decide whether a man accused of murder was guilty or innocent. If a group of people can be trusted to decide the question of a man's future, surely they should be considered sufficiently intelligent to distinguish between what matters and what does not matter. The fact that the trial was aborted indicates that neither the barristers nor the judge had a high regard for the intelligence of the jury members. The judge did not reply to my letter. I did receive an acknowledgement from an official, who said that 'it was not the practice' for judges to enter into correspondence about such matters.

My own observations of juries has convinced me that they are often not up to the task with which they are entrusted. I do not say, by any means, that juries are always incapable of understanding the evidence and of considering its significance, simply that they are too often apparently incapable of doing these things.

Why do I say this? What evidence do I have for making such a statement, given that it is not permissible to ask juries how they arrived at their conclusions? The answer is that I have known juries to arrive at verdicts that are clearly irrational. The ability to understand and to evaluate evidence is not a common attribute; and I do not mean this statement to be taken as a disparaging remark. The ability to assess evidence properly is gained over many years of training and thinking about all sorts of practical problems. Even lawyers, scientists, historians and others, whose daily work involves the assessment of evidence, often fail to 'get it right'. How much more often, then, is it likely for untrained jury members to succeed? As we have seen, most professionals (except, perhaps, retired ones) are excused jury service. Without wishing to cause any offence to members of other occupations, the fact is that most jury members are simply not equipped to cope with the demands of a trial in court.

It may seem remarkable to many people, believing that justice is administered uniformly fairly, to hear that evidence is often manipulated in court. Sometimes this manipulation is quite deliberate, but it is so often the result of confused thinking on the part of the barrister. A few examples should make the point.

Let us say that a motorist caught speeding may, on being breathalysed, register as being over the permitted limit of alcohol, when, in fact, he was not. Nothing is infallible and such a faulty result can take place. Let us say that the chance of this happening is very small; records may show that 1 per cent of the results of breathalysing tests are incorrect in this way.

In order to consider the driver's conduct in court, it will have to be stated that there is a 1 per cent chance of a positive result (i.e. that the driver had been over the limit) when, in fact, he had not been over the limit. This fact may be presented in court in a slightly different way: that there is a 1 per cent chance that the man was not over the limit, if he had got a positive result.

Are these two statements of probability the same thing? Although they look very similar, they are, in fact, not at all the same thing. Let us look at them again:

1. There is a 1 per cent chance of a positive result, when the driver was not over the limit.

2. There is a 1 per cent chance of the driver not being over the limit, if he got a positive result.

The statements are not at all the same, because the emphasis has been shifted from the probability of a positive result to the probability of the driver being over the limit. The difference may not be immediately obvious and it frequently goes unappreciated in court, especially when spoken by an able barrister. The shift in emphasis usually goes totally unnoticed, although that shift may make all the difference in the presentation of the evidence. The two statements are taken to be identical, whereas they are very different indeed, with potentially dire results.

Again, an example from everyday life should make this point very clear. Consider these two statements:

1. All dogs are four-legged animals.

2. All four-legged animals are dogs.

I think most people would see instantly that these two statements are not the same, although exactly the same words are used in each one; only their order in the sentences is different. It is also clear that one cannot possibly deduce the second from the first. Although the error in our second example is blindingly clear, whereas it may not have been so in the first example, both are the same kind of mistake, logically speaking.

Consider the following hypothetical example. If a defendant in the dock is found to have a certain type of handwriting and evidence is given that shows that, say, 85 per cent of criminals have handwriting with such characteristics, the court could easily be presented with a subtle shift in emphasis, thus:

1. 85 per cent of criminals have type A handwriting, could become

2. 85 per cent of those who have type A handwriting are criminals.

What was a statement of some interest, has become a statement of strong probability of guilt. It is easy to see how an innocent man could be convicted on such evidence, simply because of this shift of emphasis. Other examples can easily be imagined. If you, the reader, think that this is too obvious a manipulation to pass unnoticed in court, unlike the drink and drive example, remember that the two alternative statements are not presented in court clearly and separately as they are above. Indeed, they are not presented as different statements at all, one simply changes into the other as the trial progresses.

Another kind of false reasoning has caused a great deal of trouble in court. Often a psychologist will report that a child has certain attributes or exhibited certain mannerisms; say, it tended to avoid looking the psychologist in the eye or it bit its nails while it sat listening.

The child may also have told the interviewer that it had dreams of a particular kind. Referring to the results from his own and other studies, the psychologist may find that 80 per cent of abused children exhibited the first mannerism, 75 per cent exhibited the second and 90 per cent had dreams of the kind described. He would then conclude that the child he interviewed was very likely to have been abused.

Is this a valid conclusion? On the face of it, it seems reasonable enough, but closer examination will show that it is flawed. Without ever having examined an abused child, I can say, without fear of contradiction, that they all have another attribute in common: 100 per cent of abused children breathe. This attribute - breathing - is even more strongly correlated with abused children than is any one of the other attributes that led the psychologist to conclude that the child had been abused. It is not how often a particular attribute is manifested in the behaviour of abused children that matters, it is whether such a characteristic is shared by other children as well. The question that should be asked is whether, and how often, children that have not been abused also show these characteristics. In the case of breathing the answer is perfectly clear, since we all know that all children breathe. When it comes to mannerisms or dreams the answer is not so apparent; most people, including jury members, do not know how common such attributes are among children in general. The psychologist's conclusions, presented with statistical support, can appear to be rigorously scientific, when, in fact, they are not. The results and the conclusions present only half the picture; without the other half we cannot possibly arrive at a valid conclusion.

These are simple examples, but I hope to have shown that the assessment of evidence is often beyond the capabilities of many jury members. The matter is not merely of academic interest; I have known several cases of miscarriage of justice that were caused by a jury returning an irrational verdict. Grounds for appeals against a verdict cannot be made on the basis that the jury was incompetent; only new evidence or incompetence by lawyers are allowed as grounds for appeal. I agree with the Home Secretary that the time is overdue for the jury system to be examined very closely.

* Dr Zakaria Erzinglioglu has practised forensic science and given evidence in court for a period of more than twenty years.