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Expert Evidence in Criminal Courts - the Problem

Speech by Lord Justice Leveson - Forensic Science Society



There can be no doubt that whereas once, going to an expert was rare, now it is commonplace. Expert opinion evidence is only admissible on a matter calling for expertise but the field of expertise is large and ever-expanding, encompassing a range of subjects as diverse as blood tests, ear-print identification, facial mapping, voice identification, sudden infant death syndrome and lip reading; I was involved in one particular case concerning a very substantial oil spillage which led me into issues of pilotage, marine architecture and economics; I have also seen expert generated computer graphics to depict the course of a fire. Expertise has, however, proliferated in ways we ought to be careful about.

There have been increasing concerns that in certain circumstances expert evidence has been incorrectly used, or too much significance has been ascribed to it. This problem was highlighted recently by the Court of Appeal (Criminal Division) in R v Atkins [2009] EWCA Crim 1879. The Court noted three factors about expert evidence which should be borne in mind throughout. First, expert opinion is just that: an opinion. Second, experts need to know the limits of their expertise and have the integrity to inform the Court of those limits. Third, expert evidence should – indeed must – be submitted to robust testing, either by another witness in the same field or in relation to accepted scientific methodology for the science and statistical analysis for probability.


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