Letter: Verdicts and evidence in murder trials

From Mr Martin Raff

Sir: I have read and heard ofmany analyses of the jury system in the aftermath of the OJ Simpson trial, but there is one important point illustrated by the trial that seems not to have been emphasised. Jurors are rarely equipped to understand or evaluate much of the technical evidence presented. Could the jurors in the Simpson case, for example, be expected to follow the conflicting statistical arguments? And what could they have made of the two experts on EDTA [an anti-coagulant] - one of whom said there was so much EDTA in one of the blood stains that it had to have come from an EDTA-containing blood collection tube, while the other said that there was so little EDTA in the bloodstain in question that his own blood contained more? The extent of the problem was underlined by one of the dismissed jurors who, after hearing weeks of DNA evidence, remarked that she did not find this evidence convincing because she did not think it was illegal to bleed in your own home.

It seems likely that technical evidence will become even more important in trials in the future. If so, it will become increasingly important that those making decisions about guilt or innocence should be competent to evaluate this evidence. There may come a time when professionally trained jurors will be required. The OJ trial suggests that the time may be now.

Yours faithfully,

Martin Raff

MRC Laboratory for Molecular Cell Biology

University College, London

London, NW3

6 October