In Dubio Pro Reo: Behavioral Explanations of Pro-Defendant Bias in Procedures

23 Pages Posted: 16 Jan 2012

See all articles by Antonio Nicita

Antonio Nicita

University of Siena - Department of Economics

Matteo Rizzolli

LUMSA University

Date Written: September 16, 2011


The standard model of optimal deterrence predicts that the probability of wrongful conviction of innocents is at the margin as detrimental to deterrence as the wrongful acquittal of guilty individuals. We extend the model in several directions: using expected utility as well as non expected utility to consider the role of risk-aversion, non-linear probability weighting and loss-aversion. We also consider how relevant emotions such as guilt, shame and indignation play out. Several of these factors support the intuition that wrongful convictions of innocents do have a larger detrimental impact on deterrence and thus the policy implications is reconciled with the widely shared maxim that in Dubio Pro Reo. We then draw some theoretical implications such as a novel justification for the different standard of proof in criminal vs civil law as well as other policy implications.

Keywords: wrongful convictions, type-I errors, wrongful acquittals, type-II errors, evidence, optimal deterrence, behavioural economics

JEL Classification: K14, K41, K42

Suggested Citation

Nicita, Antonio and Rizzolli, Matteo, In Dubio Pro Reo: Behavioral Explanations of Pro-Defendant Bias in Procedures (September 16, 2011). Available at SSRN: or

Antonio Nicita (Contact Author)

University of Siena - Department of Economics ( email )

Piazza S. Francesco, 7
Siena, I-53100

Matteo Rizzolli

LUMSA University ( email )

Via Pompeo Magno
Roma, Rome 00191

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