The effect of verdict system on juror decisions: a quantitative meta-analysis

Elaine Jackson; Lee Curley; Fiona Leverick; Martin Lages

doi:10.1080/13218719.2023.2272912

The effect of verdict system on juror decisions: a quantitative meta-analysis

Elaine Jackson, Lee Curley, Fiona Leverick, Martin Lages^*

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

2 Citations (Scopus)

16 Downloads (Pure)

Abstract

We study the effect of the Scottish three-verdict system (guilty, not guilty, not proven) and the Anglo-American two-verdict system (guilty, not guilty) on juror decisions by combining data sets from 10 mock trials reported in suitable studies. A logistic regression with random effects uses the exact number of convictions and acquittals in 10 mock trials from a total of 1778 jurors to reliably estimate the effect of verdict system. We found a statistically significant verdict effect suggesting that the odds for a conviction by a juror are about 0.6 times or 40% lower under the three-verdict system than under a conventional two-verdict system. Possible explanations and implications of this verdict effect are discussed. This finding helps to better understand juror decision making in the context of the current reform of the Scottish three-verdict system into a two-verdict system.

Original language	English
Number of pages	19
Journal	Psychiatry, Psychology and Law
Early online date	11 Jan 2024
DOIs	https://doi.org/10.1080/13218719.2023.2272912
Publication status	E-pub ahead of print - 11 Jan 2024
Externally published	Yes

Keywords

cognitive bias
conviction rate
juror decisions
logistic regression
not-proven verdict
random effects
three-verdict system
two-verdict system

ASJC Scopus subject areas

Pathology and Forensic Medicine
Psychology (miscellaneous)
Psychiatry and Mental health
Law

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Documents and Links

10.1080/13218719.2023.2272912

Final published versionFinal published version, 1.16 MBLicence: CC BY

2 Citations
2 Article
1 Chapter (peer-reviewed)

A critique of the experimental study of juror decision-making: challenges and recommendations
Curley, L. J. & Peddie, N., 5 Jul 2024, Contemporary Challenges in the Jury System: a Comparative Perspective. Monaghan, N. (ed.). 1 ed. Routledge , p. 189-206 18 p. (Routledge Contemporary Issues in Criminal Justice and Procedure).
Research output: Chapter in Book/Report/Conference proceeding › Chapter (peer-reviewed) › peer-review
Scotland’s ‘not proven’ verdict does affect jurors decisions – but removing it may not improve rape conviction rates
Jackson, E., Leverick, F., Curley, L. J. & Lages, M., 30 Apr 2024, The Conversation.
Research output: Contribution to specialist publication › Article

Open Access
File
Jurors who believe rape myths contribute to dismal conviction rates – but judge-only trials won’t solve the problem
Curley, L. J. & Munro, J., 10 May 2023, The Conversation.
Research output: Contribution to specialist publication › Article

Open Access
File

Cite this

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title = "The effect of verdict system on juror decisions: a quantitative meta-analysis",

abstract = "We study the effect of the Scottish three-verdict system (guilty, not guilty, not proven) and the Anglo-American two-verdict system (guilty, not guilty) on juror decisions by combining data sets from 10 mock trials reported in suitable studies. A logistic regression with random effects uses the exact number of convictions and acquittals in 10 mock trials from a total of 1778 jurors to reliably estimate the effect of verdict system. We found a statistically significant verdict effect suggesting that the odds for a conviction by a juror are about 0.6 times or 40% lower under the three-verdict system than under a conventional two-verdict system. Possible explanations and implications of this verdict effect are discussed. This finding helps to better understand juror decision making in the context of the current reform of the Scottish three-verdict system into a two-verdict system.",

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author = "Elaine Jackson and Lee Curley and Fiona Leverick and Martin Lages",

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doi = "10.1080/13218719.2023.2272912",

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T1 - The effect of verdict system on juror decisions: a quantitative meta-analysis

AU - Jackson, Elaine

AU - Curley, Lee

AU - Leverick, Fiona

AU - Lages, Martin

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Y1 - 2024/1/11

N2 - We study the effect of the Scottish three-verdict system (guilty, not guilty, not proven) and the Anglo-American two-verdict system (guilty, not guilty) on juror decisions by combining data sets from 10 mock trials reported in suitable studies. A logistic regression with random effects uses the exact number of convictions and acquittals in 10 mock trials from a total of 1778 jurors to reliably estimate the effect of verdict system. We found a statistically significant verdict effect suggesting that the odds for a conviction by a juror are about 0.6 times or 40% lower under the three-verdict system than under a conventional two-verdict system. Possible explanations and implications of this verdict effect are discussed. This finding helps to better understand juror decision making in the context of the current reform of the Scottish three-verdict system into a two-verdict system.

AB - We study the effect of the Scottish three-verdict system (guilty, not guilty, not proven) and the Anglo-American two-verdict system (guilty, not guilty) on juror decisions by combining data sets from 10 mock trials reported in suitable studies. A logistic regression with random effects uses the exact number of convictions and acquittals in 10 mock trials from a total of 1778 jurors to reliably estimate the effect of verdict system. We found a statistically significant verdict effect suggesting that the odds for a conviction by a juror are about 0.6 times or 40% lower under the three-verdict system than under a conventional two-verdict system. Possible explanations and implications of this verdict effect are discussed. This finding helps to better understand juror decision making in the context of the current reform of the Scottish three-verdict system into a two-verdict system.

KW - cognitive bias

KW - conviction rate

KW - juror decisions

KW - logistic regression

KW - not-proven verdict

KW - random effects

KW - three-verdict system

KW - two-verdict system

U2 - 10.1080/13218719.2023.2272912

DO - 10.1080/13218719.2023.2272912

M3 - Article

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JO - Psychiatry, Psychology and Law

JF - Psychiatry, Psychology and Law

ER -

The effect of verdict system on juror decisions: a quantitative meta-analysis

Abstract

Keywords

ASJC Scopus subject areas

UN SDGs

Documents and Links

Fingerprint

Research output

A critique of the experimental study of juror decision-making: challenges and recommendations

Scotland’s ‘not proven’ verdict does affect jurors decisions – but removing it may not improve rape conviction rates

Jurors who believe rape myths contribute to dismal conviction rates – but judge-only trials won’t solve the problem

Cite this