Can Molecular Genetic Evidence Influence Jurors’ Perceptions of a Defendant? Results From a Randomized Experiment

• Author: Margaret Pate,Chris L. Gibson,Elise T. Costa
• DOI: 10.1177/0093854817715882
• Published date: 01 August 2017
• Date: 01 August 2017
• Subject Matter: Articles

https://doi.org/10.1177/0093854817715882

CRIMINAL JUSTICE AND BEHAVIOR, 2017, Vol. 44, No. 8, August 2017, 1101 –1119.

DOI: 10.1177/0093854817715882

© 2017 International Association for Correctional and Forensic Psychology

1101

CAN MOLECULAR GENETIC EVIDENCE

INFLUENCE JURORS’ PERCEPTIONS OF A

DEFENDANT?

Results From a Randomized Experiment

ELISE T. COSTA

University of Florida

MARGARET PATE

Radford University

CHRIS L. GIBSON

University of Florida

Despite increases in genetic evidence being used as mitigating or aggravating factors in criminal cases, few studies have

examined whether evidence of a defendant’s genotype influences legal decision making of jurors. Using a randomized

experiment, this study examined whether potential jurors’ legal decisions are affected when a defendant’s molecular genetic

information is entered as mitigating evidence. Participants served as potential jurors from two universities (N = 279). Results

from multivariate regression models suggest that genetic evidence does not influence punitive attitudes toward a defendant.

However, genetic evidence did have a statistically significant effect on fearfulness of the defendant. Participants assigned to

the condition in which evidence of the defendant possesses genetic risk of criminality and a history of child abuse were the

most fearful of the defendant. We conclude by describing how our findings are related to past research, and we also discuss

implications of our study for future research.

Keywords: biosocial; juries; courts; criminology; 5HTTLPR; DRD4

INTRODUCTION

Jury decision making is a primary component of the American criminal justice system,

and for that reason it is important to understand how genetic evidence influences potential

members of juries. Deoxyribonucleic acid (DNA) evidence has traditionally been presented

by the prosecution to place a defendant at a crime scene or by defense attorneys during the

appeal process in an attempt to exonerate a convicted client. Defense attorneys have more

recently introduced genetic evidence as a mitigating factor, arguing that a genetic predispo-

sition is partly responsible for their clients’ criminal behaviors. More than 200 cases have

AUTHORS’ NOTE: Correspondence concerning this article should be addressed to Elise T. Costa,

Department of Sociology and Criminology & Law, University of Florida, Gainesville, FL 32611; e-mail:

ecosta22@ufl.edu.

715882CJBXXX10.1177/0093854817715882Criminal Justice and BehaviorCosta et al. / Results From a Randomized Experiment

research-article2017

1102 CRIMINAL JUSTICE AND BEHAVIOR

been documented where lawyers attempted to use genetic evidence as a mitigating or aggra-

vating factor (Feresin, 2009), and genetic evidence has also been introduced in appeals for

death penalty cases (Denno, 2011). In recent years, the use of behavioral genetic evidence

has become increasingly popular. Over the 13-year period of 1994 to 2007, 48 criminal

cases have been documented applying behavioral genetic evidence (Denno, 2009), and 33

criminal cases from 2007 to 2011 (Denno, 2011). These numbers demonstrate courts’ will-

ingness to allow this type of evidence into a courtroom. Given that the use of behavioral

genetic evidence in the courtroom is occurring, it is important to know how jurors apply

genetic evidence, if at all, in their legal decision making.

Studies examining the effects of a defendant’s genetic information on sentencing out-

comes and jurors’ opinions are sparse. The few studies have suggested that (a) judges evalu-

ate defendants as being less culpable and thus willing to assign significantly lower

incarceration lengths (Aspinwall, Brown, & Tabery, 2012), (b) potential jurors are more

fearful of defendants who possess genetic propensities for violence, and (c) potential jurors

also perceive genetic evidence, when combined with environmental risk factors, as aggra-

vating, thus resulting in lengthier criminal sentences (Appelbaum & Scurich, 2014).

Our study contributes to this small body of research that has linked genetic evidence to

criminal sentencing by examining whether potential jurors’ legal decisions are influenced

by molecular genetic evidence of a defendant possessing risk alleles of DRD4 and 5HTTLPR

genetic polymorphisms that have been linked to antisocial behavior and violence (see Ficks

& Waldman, 2014). While researchers have begun to study the impact of genetic evidence

on jurors, these studies often use vague statements about the defendant’s behavior being

linked to genetic predispositions (Appelbaum & Scurich, 2014; Appelbaum, Scurich, &

Raad, 2015; Cheung & Heine, 2015). However, in real cases it is likely that the evidence

presented to jurors by an attorney or expert witness would be more complex and specific to

the genes or genotype of the defendant. Therefore, the purpose of the current study was to

explore the effects of genetic evidence on jurors’ legal decisions when that evidence is gene

specific. This study uses an experimental design to determine whether genomic explana-

tions for a defendant’s behavior influence potential jurors’ legal decisions and perceptions

of a defendant compared with other explanations. The study utilized a sample of 279 under-

graduate students from two universities who completed the study online.

GENETIC EVIDENCE IN CRIMINAL TRIALS

The American legal system has witnessed attempts to include genetic information in

legal proceedings, including the highly publicized sterilization arguments in Buck v. Bell

(1927) during the 1920s and XYY arguments in the 1960s (Appelbaum, 2014). Genetic

information has more recently become an integral part of appeals through its important role

in the exoneration of innocent defendants. While the benefits of genetic information become

apparent when used to exonerate innocent individuals, other forms of genetic information,

such as genetic mutations or polymorphisms, are new to the legal system. Thus, the extent

to which evidence of a defendant’s genotype mitigates or aggravates courtroom decisions is

largely unknown. Although DNA evidence used for exoneration has been accepted, scien-

tific evidence has shown that the linkage between genes and criminal behavior is not deter-

ministic. Thus, the court may be reluctant to accept genetic evidence as mitigating or

aggravating factor based on standards of evidence submission such as Daubert (Daubert v.

Merrell Dow Pharmaceuticals, 1993) and Frye (Frye v. United States, 1923) standards.