An English Daubert? Law, Forensic Science and Epistemic Deference

Abstract

A test for the admissibility of expert evidence, partly derived from Daubert, has recently been introduced into English criminal law by the unusual mechanism of a Practice Direction. This article compares the Daubert trilogy and the English Practice Direction as responses to the problem of epistemic deference by juries to experts. Juries are often justified in deferring to experts as to the relevance of the underlying evidence examined by the expert, including what inferences can be drawn from it. There is a concern, however, that juries may also defer to experts’ claims about the weight of their own evidence: how strongly or confidently those inferences can be stated. Overly deferential jurors may place excessive weight on forensic science evidence that rests on shaky foundations. The new English admissibility regime (drawing on recommendations by the Law Commission) appears better tailored than Daubert to address this issue about the strength of inferences presented by expert witnesses. As a result, however, it places considerable demands in judges, advocates and expert witnesses, and how successful it will be in practice remains to be seen. Introduction Until very recently, England and Wales had nothing like a Daubert test for admissibility of expert evidence. Civil judges, who normally decide cases without juries, play an active ‘gatekeeping’ role but it is focused explicitly on casemanagement and cost reduction – which are arguably the real aims of Daubert (Jacob 2009; Faigman 2013). In the criminal courts there have been few reported decisions to exclude any kind of expert evidence except that of psychiatrists or psychologists. Effective 7 October 2014, however, an admissibility test recognizably derived from Daubert has been introduced into the criminal courts by the somewhat unusual mechanism (for such a significant change) of a Practice Direction issued by the Lord Chief Justice (Thomas 2014a). As Lord Thomas has acknowledged, the Practice Direction amounts to “a novel way of implementing an excellent report” by the Law Commission, an advisory body whose proposals for a new statutory admissibility test were rejected by the government (Thomas 2014b, 6). The Commission’s report, in turn, was a response to the recommendation of a parliamentary committee that an admissibility test based on Daubert was needed to reduce the risks posed by unreliable forensic science or medical evidence (House of Commons 2005). Those risks had been highlighted by a series of notorious miscarriages of justice, including major cases of terrorism in the