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Miscarriages of Justice and the Forensic Expert: the Impact of the Law Commission's Reforms

The law’s reliance on forensic science is an inevitable necessity. The rapid evolution of new forensic methods, allied with a too-easy reliance on expert forensic opinion does, however, expose the justice system to a range of dangers. The ever-growing list of miscarriages of justice involving misplaced reliance on flawed forensic and diagnostic techniques and misguided expert witnesses has led to numerous reviews of criminal convictions by the Criminal Cases Review Commission, as well as attracting the attention of the Law Reform Commission of England and Wales. In its latest report, Expert Evidence in Criminal Proceedings in England and Wales, the Commission notes (at para 1.17) that “expert evidence of doubtful unreliability is being proffered for admission, and placed before the jury, too readily. . . . It has even been suggested that there may be a ‘culture of acceptance’ on the part of some trial judges”. The Commission has, consequently, proposed a statutory consolidation of the various common law rules governing the admissibility of expert opinion evidence in criminal cases, together with proposals for a new “reliability test”, allied with further guidelines for trial judges. In doing so, the Commission has sought to introduce legislative changes which go far beyond anything suggested in any other Anglo-American legal system and are likely to have a profound effect on the use of expert witnesses in the courts of England and Wales. It may be noted at this stage that the main thrust of the Law Commission’s proposals relate to scientific and medical expert opinion, although these will naturally overlap with expert opinion in other areas (for instance, lip-reading techniques and forensic accountancy). The miscarriages of justice which have been reviewed by the appellate courts in recent decades fall into a number of categories. The first of these have, regrettably, involved cases where the expert witness has deliberately misled the court, as demonstrated by cases such as Maguire and Ward. In the former case, the Court of Appeal noted that the forensic scientist in question, employed by the Royal Armament and Research Development Establishment Laboratory, had deliberately misled the court as to the accuracy of a test known as thin-layer chromatography, used to test the presence of nitro-glycerine. In the latter case, the Court of Appeal identified the major cause of the injustice as arising from the fact that three government forensic scientists had failed to disclose material evidence in their pro-prosecution partisan approach adopted at trial. The second category of cases involves expert witnesses who stray outside their discipline and opine on matters where their expertise is limited. A case in point is Clarke, whose conviction for the murder of her two infant sons was finally quashed in 2003. The chief prosecution witness, who was a professor of paediatrics and child health (i.e. not a statistician), nonetheless provided expert opinion based on unreliable statistical evidence. His opinion, given to the trial court in a dogmatic manner, was that there was only a one in 73 million chance of two natural cot deaths (SIDS – sudden infant death syndrome), in the circumstances of this particular kind of case. The Court of Appeal, in its criticism of the manner in which the witness had strayed outside his own discipline, noted that it was “unfortunate that the trial did not feature any consideration as to whether the statistical evidence should be admitted in evidence”. Medico-Legal Journal (2011) Vol. 79 Part 3, 94–99. DOI: 10.1258/mlj.2011.011019 # Medico-Legal Society 2011 94