LAST WEEK scientists in America announced that they have found strong evidence that cot death ? sudden infant death syndrome ? is caused, in part, by a genetic disorder.

The study, funded by the United States National Institute of Health, found that cot-death babies have abnormalities in those parts of the brain that control breathing, heart rate, blood pressure and arousal.

These views, of course, starkly contrast with the now repudiated opinion of Professor Sir Roy Meadow in the case of Sally Clark, who was wrongly convicted of murdering her two sons. Sir Roy was of the view that one cot death was a tragedy, two suspicious and three murder, unless proven otherwise. He also gave evidence to the effect that there was a 1:73 million chance that two children in the same family would die of cot death. So, proof yet again, if further proof were needed, that research can undermine accepted wisdom or even stand it on its head.

Last month three Court of Appeal judges upheld the High Court decision that Sir Roy was not guilty of serious professional misconduct. However, the appeal court overturned the High Court ruling that expert witnesses should be exempt from disciplinary action by their regulatory body. This is a welcome development. It may seem odd that the court grants immunity to the expert that can then, in effect, be removed by a professional regulatory body such as the General Medical Council (GMC). The decision may also have the effect of deterring doctors and other professionals from giving expert evidence. However, as Finlay Scott, chief executive of the GMC, said, the public must be confident that doctors and other professionals who give evidence in court proceedings can, if necessary, be held to account by their regulator.

Last week brought another welcome development in the announcement by Sir Liam Donaldson, the Chief Medical Officer, that a central NHS register of expert witnesses should be created to help to prevent miscarriages of justice and to ensure the availability of willing and properly qualified experts. Under the proposed system, experts will not be recruited through solicitors but through an NHS national knowledge service. Specialist doctors and other NHS professionals will come together and improve the quality of service through mentoring, supervision and peer review. Such a system should go a long way towards avoiding the risk of reports for the courts being biased by the views of a particular individual or flawed by a lack of expertise.

Welcome as these recent developments are, however, the ultimate safeguard is still missing because, remarkably, English law reflects a general reluctance to impose, as a condition of the admissibility of expert evidence, a requirement of reliability having regard to the techniques or theories on which it is based.

In 2001 the Court of Appeal expressed the view that the English approach accorded with the guiding principle in America, as stated in Frye v the United States, that expert evidence based on novel or developing scientific techniques that are not generally accepted by the scientific community should be excluded.

In fact, that test was not then, and is not now, the guiding principle in the US. The Supreme Court has since ruled, in the celebrated case of Daubert v Merrell Dow Pharmaceuticals, that the ?general acceptance? test is not good law in the federal courts: federal courts must ensure the reliability as well as the relevance of scientific evidence before admitting it; and reliability should be determined having regard to a number of factors, including whether the technique can be and has been tested, whether it has been the subject of publication and peer review, its error rate and whether it is generally accepted.

More recently the English Court of Appeal appears to accept that reliability can be relevant to admissibility. Yet it has approved the admissibility of ear-print evidence, even though the expertise for ear- print comparison is in its infancy and without regard to the Daubert factors, none of which would have supported the case for admission. Similarly, in another case, the Court of Appeal has rejected the argument that lip-reading evidence should not be admitted unless it can be seen to be reliable.

The obvious danger of this relaxed approach is that it will lead to more miscarriages of justice. In 1991, in an English case, a lecturer in phonetics gave an opinion on the identity of a voice although his technique was not generally respected by other experts because it was not supplemented or verified by acoustic analysis based on physical measurements. In 2003, in Northern Ireland, similar evidence was given, but an appeal succeeded because fresh expert evidence showed that on acoustic analysis the voice in the case was not that of the accused.

Expert evidence is received to provide expertise that the fact-finders do not have. The purpose is to assist them to reach the right decision. The continuing reception of unreliable expert evidence simply defeats that purpose.

The author is Professor of Law, the City Law School, City University London, and author of The Modern Law of Evidence, 6th edn, Oxford University Press