Does Psychopathy Influence Juror Decision-Making in Capital Murder Trials? “The Devil is in the (Methodological) Details”

• Author: Shannon E. Kelley,John F. Edens,Tiffany N. Truong
• Date: 01 May 2021
• Published date: 01 May 2021
• DOI: 10.1177/0093854820966369
• Subject Matter: Articles

CRIMINAL JUSTICE AND BEHAVIOR, 2021, Vol. 48, No. 5, May 2021, 690 –707.

DOI: https://doi.org/10.1177/0093854820966369

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© 2020 International Association for Correctional and Forensic Psychology

690

DOES PSYCHOPATHY INFLUENCE JUROR

DECISION-MAKING IN CAPITAL

MURDER TRIALS?

“The Devil is in the (Methodological) Details”

TIFFANY N. TRUONG

Texas A&M University

SHANNON E. KELLEY

William James College

JOHN F. EDENS

Texas A&M University

Concerns about the potentially stigmatizing impact of psychopathy evidence in court have been expressed for decades. Saks

et al. manipulated diagnostic information (e.g., psychopathy, schizophrenia) and the basis for that evidence (e.g., clinical,

neuroimaging) to examine effects on outcomes in two capital murder case vignettes. Somewhat surprisingly, their psychopa-

thy manipulation did not have a consistently adverse impact on juror attitudes relative to other diagnoses or a control condi-

tion. We administered the Saks et al. stimulus materials to college students (N = 569), but added a scale quantifying

participant ratings of how psychopathic they perceived the defendant to be. Notably, we obtained uniformly high mean

psychopathy ratings across all study conditions. In addition, participants who rated the defendant as more psychopathic

(regardless of condition) were more likely to support death verdicts. We discuss the implications of our results in terms of

the design of experimental manipulations of mental health evidence for jury simulations.

Keywords: psychopathy; mock jurors; replication; mental health evidence; internal validity

Psychopathic personality disorder (psychopathy) is characterized by several socially

undesirable traits, such as remorselessness, lack of empathy, manipulativeness, and irre-

sponsibility (Patrick, 2018). Over the years, the label “psychopath” and its associated traits

have been introduced into a diverse array of legal proceedings, often to support prosecution

claims that a defendant is dangerous and/or untreatable (Blais, 2015; DeMatteo, Edens,

AUTHORS’ NOTE: We thank Dr. Michael Saks and colleagues for their willingness to share detailed informa-

tion concerning their study design and stimulus materials. This attempted replication would not have been

possible without their helpful input. Correspondence concerning this article should be addressed to John F.

Edens, Department of Psychological and Brain Sciences, Texas A&M University, TAMU 4235, College Station,

TX 77845; e-mail: johnedens@tamu.edu.

966369CJBXXX10.1177/0093854820966369Criminal Justice and BehaviorTruong et al. / PSYCHOPATHY AND CAPITAL PUNISHMENT

research-article2021

Truong et al. / PSYCHOPATHY AND CAPITAL PUNISHMENT 691

Galloway, Cox, Smith, & Formon, 2014; DeMatteo, Edens, Galloway, Cox, Smith, Koller,

et al., 2014; Edens & Cox, 2012; Viljoen, MacDougall, et al., 2010; Viljoen McLachlan, &

Vincent, 2010) in cases in which the consequences for the defendant can be profound (e.g.,

denial of discretionary release, severe deprivations of liberty, and death sentences).

Forensic mental health evaluators typically operationalize psychopathy using the

Psychopathy Checklist–Revised (PCL-R; Hare, 2003). Some psychology-law scholars have

described the PCL-R as a “prosecution tool” (DeMatteo, Edens, Galloway, Cox, Smith,

Koller, et al., 2014, p. 96) in that, in the vast majority of cases, it is the prosecution that seeks

to introduce it into evidence. Although some legal scholars have written about the potential

exculpatory or mitigating role that psychopathy evidence might play in criminal cases (e.g.,

Morse, 2008, 2013), and there are anecdotal examples of defense counsel attempting to use

the PCL-R in mitigation, survey results from defense team members suggest that it is rela-

tively rare for the defense to call an expert mental health witness to proactively introduce

PCL-R evidence in criminal cases (Edens & Cox, 2012). When such witnesses do testify

about psychopathy, it is typically in rebuttal to prosecution-retained experts who have testi-

fied about PCL-R evaluations in support of a legal opinion that is to the detriment of the

defendant (e.g., that the defendant deserves a death sentence).

Using psychopathy evidence in an attempt to influence legal decision-making has gener-

ated considerable controversy over the years (Edens et al., 2018). For example, numerous

field studies published in the past 10 to 15 years—based primarily although not exclusively

on sex offender cases—have questioned whether PCL-R total and subscale scores provided in

adversarial contexts are sufficiently reliable to justify their admissibility in court (Boccaccini,

Turner, & Murrie, 2008; Edens et al., 2010; Edens et al., 2015; Miller et al., 2012; Sturup

et al., 2014), particularly given evidence that examiners retained by the defense produce on

average much lower PCL-R scores than those retained by the prosecution (DeMatteo, Edens,

Galloway, Cox, Smith, & Formon, 2014; DeMatteo, Edens, Galloway, Cox, Smith, Koller,

et al., 2014; Edens et al., 2015; Murrie et al., 2008, 2013, 2009). Other, more specific reserva-

tions have been raised about the probative value of using psychopathy evidence to address

certain legal questions concerning a defendant’s mental health status. For example, high

PCL-R scores have been offered in court to rebut defense evidence that defendants suffer from

(potentially mitigating or exculpatory) mental disorders (e.g., schizophrenia, intellectual dis-

abilities), as well as to support prosecution claims that defendants are malingering severe

mental disorder (DeMatteo, Edens, Galloway, Cox, Smith, Koller, et al., 2014).1

Given the socially undesirable nature of the traits associated with psychopathy, another

controversy relates to the extent to which labeling a defendant as “a psychopath” might be

unduly stigmatizing in criminal cases. Since the early 2000s, research has investigated how

laypersons respond to psychopathy evidence that is introduced by prosecution-retained

expert witnesses and whether such responses might result in unfair prejudice (see, for

example, Federal Rules of Evidence). This research typically involves simulation designs

based on vignettes in which mock jurors review case facts and experimentally manipulated

mental health evidence prior to providing opinions about appropriate outcomes (e.g.,

verdicts, sanctions) and perceptions of the defendant (e.g., as being dangerous, in need of

treatment, responsible for their actions, or “evil”).

Most case vignette simulations suggest that mock jurors who view defendants as highly

psychopathic tend to respond more negatively to them than do those jurors who do not view

hypothetical defendants as particularly psychopathic (Edens et al., 2005). A recent meta-

analysis of this literature (Kelley et al., 2019) examined the association between perceived