Scottish jury research - mock jury study: summary of findings

Key Findings

The overarching finding is that verdicts were affected by how the jury system was constructed. The research found that the number of jurors, the number of verdicts available, and the size of majority required do have an effect on verdict choice. In other words, jurors' verdict preferences are not simply a reflection of their assessment of the evidence presented, but can also be affected by features of the jury system within which this evidence is considered.

Taken together, the main findings from this study suggest that:

• Reducing jury size from 15 to 12 might, in some trials, lead to more individual jurors switching their position towards the majority view (whether to acquit or convict) to facilitate a verdict.
• Asking juries to reach a unanimous or near unanimous verdict, rather than a simple majority verdict, might tilt more jurors in favour of acquittal – and might, therefore, lead to more acquittals over a larger number of finely balanced trials.
• Removing the not proven verdict might incline more jurors towards a guilty verdict in finely balanced trials – and might, therefore, lead to more guilty verdicts over a larger number of trials.

In terms of the impact of potential changes on how juries reach their decisions:

• Reducing jury size from 15 to 12 might lead to more jurors participating more fully in the deliberations and is unlikely to have much impact on deliberation length or the range of evidential or legal issues discussed.
• Requiring juries to reach a unanimous or near unanimous verdict, rather than a simple majority verdict as they do currently,is likely to increase the average deliberation time, and may result in jurors being more likely to feel they have had the opportunity to put their views across before a verdict is reached. However, this may not lead to any improvement in the range of evidential or legal issues discussed.
• Removing the not proven verdict is unlikely to have much impact on key aspects of the jury decision-making process, such as deliberation length or juror participation, but may be associated with a slight increase in juror dissatisfaction.
• The combination of features that produced the most jurors in favour of a guilty verdict after deliberating was 15-person, simple majority, two-verdict juries. In contrast, the combination which produced the lowest number of individual guilty verdicts was 12-person, unanimous, three-verdict verdict juries.
• There were inconsistent views on the meaning of not proven and how it differed from not guilty. Although the not proven verdict was seldom discussed during deliberations, when it was discussed those who favoured it tended to base this on a belief that the evidence did not prove guilt beyond reasonable doubt, or on the difficulty of choosing between two competing accounts. Jurors choosing the not guilty verdict (where not proven was also an option), on the other hand, tended to attribute this to a belief that the accused was innocent.

Other cross-cutting key findings on how juries reach decisions include:

• Several potential misunderstandings of legal concepts arose relatively frequently across the mock juries. For example, there was a belief that the accused needed to prove their innocence, a belief that the accused can be retried following a not proven verdict but not a not guilty verdict, and misunderstanding of the fact that self-defence is a legitimate defence to an assault charge, even when the fact the accused inflicted the injury is not in dispute. This raises important questions about what can be done to support jurors' understanding of legal issues, including their understanding of the meaning and effects of the not proven verdict.
• Additional guidance such as written routes to verdict or written reminders of key legal principles may be helpful to aid jurors' discussion. Methods for improving juror understanding are discussed more fully in J Chalmers and F Leverick, Methods of Conveying Information to Jurors: An Evidence Review (2018).