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Research highlights effects of unique Scottish jury system

9 October 2019

The size of a jury, the number of verdicts available and the type of majority required may all have an effect on the outcome of finely balanced trials, according to groundbreaking research into how juries reach decisions.

The study, “the largest and most realistic of its kind ever undertaken in the UK”, according to Justice Secretary Humza Yousaf at the launch of the report, examined the effect of the three distinctive features of Scotland’s jury system which have come under scrutiny in recent years. Those are the size of the jury – 15, as opposed to 12 in most English speaking jurisdictions; the giving of verdicts by a simple majority; and the availability of the not proven verdict, in addition to guilty and not guilty.

It was carried out as recommended by retired judge Lord Bonomy, in his report on safeguards that might be needed if the rule requiring corroborated evidence for a conviction, was to be abolished. The research was carried out by Ipsos MORI Scotland along with Professor James Chalmers and Professor Fiona Leverick of the University of Glasgow, and Professor Vanessa Munro of the University of Warwick.

In the research, 64 mock juries using 863 volunteers, representing a cross section of the population, had to view a video of one of two mock but realistic trials – an assault case and a rape case – and consider their verdict. The juries were divided between those with 15 and those with 12 members, those able to reach a majority decision and those requiring to be unanimous, and those with three verdicts available and those with only two. Jurors had to complete a questionnaire before and after their deliberations.

Among the key findings were:

  • reducing the jury size from 15 to 12 might lead to more individual jurors switching their position towards the majority view – though they might be less inclined to do so if that is for a guilty verdict;
  • asking juries to reach a unanimous or near unanimous verdict might tilt more jurors in favour of acquittal, and did not lead to any improvement in the range of evidential or legal issues discussed;
  • removing the not proven verdict might incline more jurors towards a guilty verdict in finely balanced trials. Juries almost always chose not proven in preference to not guilty when they wanted to acquit the accused.

The combination of features most likely to produce a guilty verdict was a 15 person, simple majority, two verdict jury, while most likely to acquit was a 12 person, unanimous, three verdict jury.

The study found some misunderstanding of the not proven verdict even after the directions by the trial judge, including that an accused could be retried after such a verdict.

Commenting on the research, Mr Yousaf said:

“I am grateful to everyone who gave up their time for this major piece of research, which is just one part of our work to improve Scotland’s justice system for all.

“We will now engage with legal professionals and the wider public to consider all of the findings. We are organising events around the country and I am keen to hear from a wide range of people, especially those with personal experience of the criminal justice system.

“In particular, we will now engage in serious discussions on all of these findings including whether we should move to a two verdicts system. My mind is open and we will not prejudge the outcome of those conversations.”

Click here to access the report.


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