This final chapter summarises the conclusions that can be drawn from this study with respect to the two key research questions:
- What effects do the unique features of the Scottish jury system (majority, size and the three-verdict system) have on jury reasoning and jury decision-making?
- What are jurors' understandings of the not proven verdict and why might they choose this verdict over another verdict?
Each of the three unique features of the Scottish jury system - 15 members, simple majority verdicts, and the availability of the not proven verdict - is discussed in turn, along with the potential implications of any changes to those features.
6.1 What effects do the unique features of the Scottish jury system have on jury reasoning and jury decision-making?
6.1.1 What impact do the unique features have on verdict choice?
At jury level, there were no statistically significant differences in the proportion of guilty versus acquittal verdicts returned between juries that had the not proven verdict available and juries that did not, between 12 and 15-person juries, or between juries asked to reach a unanimous verdict and those asked to reach a simple majority. This is unsurprising given the sample size.
There were, however, a number of statistically significant differences in verdict preferences of individual jurors, namely that:
- When the not proven verdict was available, more individual jurors favoured acquittal. This difference was apparent both before and after deliberation - in other words, the availability of not proven was associated with individual jurors being less likely to favour a guilty verdict, independently of any impact of deliberating as a group.
- Jurors in 15-person juries were less likely to change their minds on the verdict than jurors in 12-person juries. Although jurors in 15-person juries were more likely to think the verdict should be guilty (after deliberating) than were jurors in 12-person juries, this does not necessarily indicate that 15-person juries would be more likely to return guilty verdicts across a larger number of differently balanced trials. Rather, it is a reflection of the related finding that jurors in 15-person juries were less likely to change their initial view on the verdict than jurors in 12-person juries. The reason for this may simply be one of jury dynamics - in a 15-person jury, on average more people would need to shift their position to change the outcome. There may, therefore, be less motivation for 'minority' jurors in a 15-person jury (which in this case was usually those who favoured guilty) to shift that position to bring deliberations to a close.
- Whilst jurors who were asked to reach a simple majority were more likely to think the verdict should be guilty (after deliberating) than those who were asked to reach a unanimous verdict, this does not necessarily imply that requiring unanimity would result in fewer guilty verdicts. It might simply reflect a greater tendency among jurors who favour a minority verdict at the outset to move towards the majority position during deliberations. However, there is evidence to suggest that jurors may be less willing to move from acquittal to guilty when the initial balance of opinion is the other way around - five of the six unanimity juries that started out with a majority for guilty ended up hanging, compared with one of the 25 unanimity juries that started with a majority for acquittal.
Taken together, these findings suggest that:
- Reducing jury size from 15 to 12 might, in some trials, lead to more individual jurors switching their position to facilitate a verdict.
- Moving from requiring juries to reach a simple majority to requiring unanimity or near unanimity might tilt more jurors in favour of acquittal - and might, therefore, lead to more acquittals over a larger number of trials.
- Removing the not proven verdict might incline more jurors towards a guilty verdict - and might, therefore, lead to more guilty verdicts over a larger number of trials.
It is not possible, based on these findings, to estimate the likely scale of any impact on the verdicts juries reach arising from changing these features, since the precise effect will depend on other factors including the balance of evidence and the initial balance of opinion in the jury in each trial. However, analysis of interactions between the different features suggests that the feature that makes the most difference to individual juror views on the verdict is the majority required. Moreover, this is the only difference that was statistically significant across both the rape and the assault trial juries - jury size and the number of verdicts available were significantly associated with individual verdict preferences in the assault trial only.
The combination of features most likely to tilt jurors towards acquittal appears to be 12-person, three-verdict, and unanimity required, while the combination most strongly associated with jurors favouring a guilty verdict is 15-person, two-verdict, simple majority. Neither of these is the system currently employed in either Scotland or most other English language jurisdictions. However, the latter would be the system in Scotland if the not proven verdict were removed with no other changes being made.
6.1.2 What impact do the unique features have on how juries reach decisions?
15-person juries were associated with somewhat lower levels of juror participation than 12-person juries across a number of measures. For example:
- Jurors were more likely to be observed wanting to contribute, but being unable to do so in 15-person juries.
- There were more dominant jurors and more minimally contributing jurors, on average, in 15-person juries.
- Jurors in 15-person juries were more likely to agree that "some members of the jury talked too much".
- Jurors in 15-person juries gave lower ratings of their own influence over the verdict.
- When reviewing 15-person juries, it was common for researchers to note the existence of side conversations running concurrently within discussions, and for them to comment on the existence of higher levels of interruption and speaking over one another, which was perceived to lead to a less ordered deliberation overall.
However, the higher level of juror participation in 12-person juries was not associated with longer deliberations (there was no difference in deliberation length by jury size) or with any increase in the number of evidential issues discussed or with the extent or accuracy of discussion of legal issues.
In contrast, the majority required did make a significant difference to how long juries deliberated: juries asked to reach a unanimous verdict took substantially longer over deliberations than did those required to reach a simple majority. In terms of juror participation, there were no significant differences in observed levels of juror participation by majority required. However, there were some differences in jurors' own perceptions of their involvement, all of which indicated that those who had been asked to reach a unanimous verdict were a little more likely to feel they had been fully involved and had influenced the decision. Requiring juries to reach unanimity may thus provide more opportunity for everyone to feel that they have been able to put their views across before a verdict is reached. This does not seem to be associated with any increase in the range of evidential issues discussed or the extent or accuracy of discussion of legal issues, however.
The presence or absence of the not proven verdict appeared to have little impact on the key aspects of the decision-making process examined in this research. There were no differences in: the length of time taken to reach a verdict; the mean number of evidential issues raised; the extent or accuracy of the discussion of legal issues (other than discussion of the not proven verdict itself); or levels of juror participation across various measures. However, jurors asked to choose between two verdicts were slightly more likely to say they had been dissatisfied with the experience than jurors who had three verdicts available. This suggests that there might be a small increase in juror dissatisfaction if not proven were not available.
Taken together these findings suggest that:
- 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.
- Moving from requiring juries to reach a simple majority to requiring unanimity or near unanimity would be likely to increase the average deliberation time (although we cannot say by how much, as the maximum deliberation time was limited to 90 minutes for the purposes of this research), 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 actually 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.
6.2 How do jurors understand the not proven verdict?
Across the 32 mock juries that had not proven as a verdict option, the meaning and consequences of the not proven verdict were rarely discussed at any length during deliberations, even in juries where that verdict was returned. Where the not proven verdict was discussed, however, there was evidence of jurors holding inconsistent understandings of what the verdict meant along with some confusion over its effect. In particular, jurors expressed uncertainty as to how it differed (if at all) from a not guilty verdict.
Although not proven and not guilty have the same effect in law, jurors tended to give different reasons for choosing them. Those who favoured the not proven verdict 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 or to some aspect of the complainer's or witness' evidence that suggested that they were not giving a truthful account.
The idea that the not proven verdict should be used when jurors think that the accused is probably guilty but that this has not been proven to the necessary standard arose frequently, albeit briefly, in deliberations. It was also the issue on which there was the clearest agreement in questionnaire responses. Jurors also expressed the (related) view that there would be a lingering stigma attached to receiving a verdict of not proven.
6.3 Other implications: supporting juror understanding
As discussed above, there is no evidence from this study that changing one or more of the unique features of the Scottish jury system would have an impact on the number of evidential issues or on the extent or accuracy of legal issues discussed during deliberations.
However, the findings do raise important questions about what can be done to support juror understanding of legal issues, including their understanding of the meaning and effects of the not proven verdict. Several potential misunderstandings on the part of individual jurors (e.g. a belief that the accused should prove their innocence, or a belief that the accused can be retried following a not proven verdict but not a not guilty verdict) arose relatively frequently across the mock juries. This suggests that there may be a need to consider whether jurors require additional guidance (such as written routes to verdict or written reminders of key legal principles) to aid their discussion. A more detailed consideration of this issue can be found in another strand of this research, which involved an extensive evidence review of ways in which juror communication methods might be improved: see J Chalmers and F Leverick, Methods of Conveying Information to Jurors: An Evidence Review (2018).
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