Jury decision making

2017-2019

Researchers: James Chalmers and Fiona Leverick, with Ipsos MORI Scotland and Vanessa Munro (University of Warwick)

This major research project, funded by the Scottish Government, examined various aspects of the way in which juries reach their decisions in criminal trials. The project stemmed from the 2014 Post-Corroboration Safeguards Review (PCSR) led by Lord Bonomy, which considered whether additional safeguards against wrongful conviction might be needed in Scotland if the longstanding requirement for corroboration in criminal cases were to be abolished (as was recommended by the Carloway Review in 2011). A number of possible safeguards were considered by the PCSR, including reform of aspects of the jury system, but it recommended that a programme of research into jury reasoning and decision making should first be undertaken in order to inform any future decisions. This research is necessary because Scottish juries have a number of distinctive features – they return verdicts by a simple majority of votes, have fifteen members and have three possible verdicts open to them (guilty, not guilty, and not proven) – which mean that much existing research is of limited applicability in the Scottish context.

The project had two components. The first addressed a number of research questions relating to the distinctive features of the Scottish criminal jury, namely:

  • What jurors understand to be the difference between not guilty and not proven;
  • Why they choose one over the other;
  • Why, and to what extent, do jurors alter their position as regards not proven and not guilty as a result of deliberations;
  • The extent to which the members of a jury of 15 (as compared with a jury of 12) actually participate in deliberations;
  • The differences in outcome (assuming an identical factual matrix) as between a 12 person jury with only 2 possible verdicts and a 15 person jury with 3 verdicts, and the reasons for those differences; and
  • Whether there are benefits in requiring the jury to attempt to reach a unanimous verdict.

These questions were all addressed via a large scale programme of mock jury experiments in which members of the public were recruited to participate in simulated jury trials. The project report was published in 2019 and links can be found below.

A parallel component of the research addressed two additional questions, namely (a) what are the most effective approaches for aiding jury comprehension of trial proceedings and the evidence presented and (b) whether jurors perceive pre-recorded evidence given by children and vulnerable witnesses differently from evidence given in a court. These questions, which are not contingent on the particular features of the Scottish jury, were addressed via reviews of existing research evidence. This component was completed in 2018 and links to the published evidence reviews can be found below.

Further work is currently ongoing, both on the implications of the project findings and on additional analysis of the project data.

Key publications:

R Ormston, J Chalmers, F Leverick, V Munro and L Murray, Scottish Jury Research: Findings from a Large Scale Mock Jury Study (2019). A summary Research Findings document is also available.

J Chalmers and F Leverick, Methods of Conveying Information to Juries: An Evidence Review (2018). A summary Research Findings document is also available.

V Munro, The Impact of the Use of Pre-Recorded Evidence on Juror Decision-Making: An Evidence Review (2018). A summary Research Findings document is also available.

F Leverick, "Jury instructions on eyewitness identification evidence: a re-evaluation" (2016) Creighton Law Review 555-588.

J Chalmers, "Jury majority, size and verdicts". In J Chalmers, F Leverick and A Shaw (eds), Post-Corroboration Safeguards Review: Report of the Academic Expert Group (2014) 140-163.

F Leverick, "Jury directions". In J Chalmers, F Leverick and A Shaw (eds), Post-Corroboration Safeguards Review: Report of the Academic Expert Group (2014) 101-117.