A persecution of the best evidence

This book surveys the psychological literature on eyewitness evidence and the legal safeguards against errors of identification. It is far more accessible to the legal world than most texts of this kind, and usefully describes the strengths and weaknesses of psychological methodology. It would make an ideal textbook for undergraduate courses on forensic psychology or the law of evidence. All the legal cases referred to are American, but the reasoning is relevant to British courts.

The underlying offensive against identification evidence is familiar, but, like many others, fails to address the central dilemma facing criminal practitioners, that, logically, eyewitness evidence is the best evidence. It is more direct than circumstantial evidence. The witness to the offence is available for cross-examination. For 25 years psychologists have waged war on the eyewitness through a massive body of literature, which has influenced British and American courts, but failed to indicate more reliable sources of evidence. Nor is the case against identification evidence proven. Assumptions are constantly made, as here. For example, research that compared verdicts against the opinions of lawyers or against newspaper and magazine articles apparently justifies a "confident conclusion" of wrongful conviction in about 500 cases in the United States.

The authors concede that results obtained in experimental conditions might not be generalisable to real crimes, but reassure themselves on an unconvincing argument. This to some extent relies on the stress studies, themselves open to the ob-jection that experimenters cannot, ethically, subject people to significant stress. It also fails to note J. C. Yuille and J. L. Cutshall's study of genuine witnesses to a street shooting, who gave accurate and detailed information, and particularly if they suffered severe stress.

There is no explanation given either for some startlingly contradictory empirical results. Line-up studies are quoted to support the doomsday scenario, with only about 46 per cent correct identifications. Later, however, where the discussion shifts to comparison of recognition accuracy between different age groups, success rates of 88 per cent to 93 per cent among eighth and 11th-grade Florida schoolchildren are mentioned without comment. Elsewhere the authors refer to findings that very attractive or unattractive faces are easier to recognise than neutrally rated ones. This factor or others might explain the disparate results obtained in many recognition studies, but there is no attempt at a connection here.

One of the book's strengths lies in a well-argued reply to the frequent criticism that psychology only discovers what we already know. A strong case is made for basing decisions on the results of scientific observation rather than instinctive reactions. Common sense is unlikely to predict, for example, the devastating effect concealment of the hairline has on recognition - hats are shown to be powerful disguises. It seems lay persons are not in fact instinctively sensitive to factors that influence eyewitness identification accuracy, and lawyers so far are only half-informed on the subject.

The book provides little cheer for those it persuades to distrust eyewitness evidence. The authors cannot identify an effective way of making jury verdicts more reliable. Expert evidence on identification has not been proved to have this effect, and curiously, using a court-appointed expert to indicate its weaknesses appears to have less impact than a defence expert operating within the adversarial tradition. To give the jury a warning from the bench, as directed by the Court of Appeal in Turnbull, makes no apparent difference to the outcome, apart from confusing the jury. The authors cannot be blamed for the gloominess of this picture. However, a little more objectivity, not necessarily reaching outright scepticism, about the research that gives rise to it, would have been welcome.

Jenny McEwan is professor of law, Keele University.