Our recent study of the way in which jurors assess credibility in criminal trials has been the subject of some attention in Scottish Legal News. In this study, we reported on the findings of a large-scale mock jury study in respect of the cues that jurors use to assess witness credibility. We found plenty of evidence of good practice in this respect. We also found an inappropriate reliance on the body language of witnesses to draw inferences about their truthfulness.

In the 31 August 2022 SLN article Juries should be told to ignore body language, academics argue, Thomas Ross QC claimed that “the conduct of pretend jurors in a small sample of pretend trials is being used as an argument to abolish [jury trial]” and replace it “with the trial system in North Korea and Saudi Arabia”. (We did not argue for trials without juries, only for rethinking one line in the standard directions currently given to juries.) The following day, in Mock trials no substitute for the real thing, Douglas Cusine wrote that “in the latest research into body language, it is suggested, rather bizarrely in my view, that jurors should be directed to ignore body language”. (Actually, our paper suggested that directing jurors to ignore body language would be unhelpful and perhaps even harmful.)

Our research is, indeed, based on mock trials. These do provide valuable evidence about how jurors in real trials would assess witness credibility. Mr Ross suggests that our jurors were more likely to rely on body language because they knew that if an actor “was fidgeting or licking his or her lips, as there was absolutely nothing for an actor to be nervous about, then presumably the pretend jurors could easily discount nerves as an explanation”. But this was not true – in 27 of the 64 trials, jurors did draw on the “nervousness” of the witnesses when assessing their credibility. There is no magic wand that suddenly changes the beliefs held by jury eligible members of the public (as our jurors were) when they go into a real jury room. The Jury Manual recommends that Scottish jurors be directed that they can look at body language to assess credibility, so it is hardly surprising that our jurors did so. They were conscientiously following the directions they had been given.

We suspect that we will not succeed in persuading either Mr Ross or Mr Cusine that mock jury research is valuable. But even if we do not, we would like to correct the record about our recommendations. Our rather mild suggestion in the paper is that “we should certainly not be specifically directing jurors – as judges currently do in the Scottish courts – to pay attention to factors such as body language in assessing witness credibility”. Nowhere do we suggest that jurors be directed to ignore it. In fact, we said that “simply directing jurors to ignore behavioural cues is unlikely to be productive (and may even, perversely, turn their attention more towards them)”. And we certainly do not suggest in the paper that juries be abolished. What we do suggest (again, we thought uncontroversially) is that jurors may benefit from more assistance in understanding what factors are useful in assessing credibility.

And the idea that body language is a good indication of truthfulness is a false belief. Eye contact (or the lack of it), fidgeting, hand movements and other bodily ‘tics’ are not accurate ways of assessing credibility, as demonstrated by the vast array of research we outline in the paper. Failing to address these false beliefs risks inaccurate trial outcomes – whether this means acquitting the factually guilty or convicting the factually innocent. We are sure that both Mr Ross and Mr Cusine would agree that this is not a desirable outcome.

James Chalmers and Fiona Leverick are professors at the University of Glasgow. Their co-author, Vanessa Munro, is on holiday. After reading recent articles, they wish they were too.