How objective are forensic experts when they are retained by one of the opposing sides in an adversarial legal proceeding? Despite long-standing concerns from within the legal system, little is known about whether experts can provide opinions unbiased by the side that retained them. In this experiment, we paid 108 forensic psychologists and psychiatrists to review the same offender case files, but deceived some to believe that they were consulting for the defense and some to believe that they were consulting for the prosecution. Participants scored each offender on two commonly used, well-researched risk-assessment instruments. Those who believed they were working for the prosecution tended to assign higher risk scores to offenders, whereas those who believed they were working for the defense tended to assign lower risk scores to the same offenders; the effect sizes (d) ranged up to 0.85. The results provide strong evidence of an allegiance effect among some forensic experts in adversarial legal proceedings.

We know surprisingly little about the interrater reliability of forensic psychological opinions, even though courts and other authorities have long called for known error rates for scientific procedures admitted as courtroom testimony. This is particularly true for opinions produced during routine practice in the field, even for some of the most common types of forensic evaluations-evaluations of adjudicative competency and legal sanity. To address this gap, we used meta-analytic procedures and study space methodology to systematically review studies that examined the interrater reliability-particularly the field reliability-of competency and sanity opinions. Of 59 identified studies, 9 addressed the field reliability of competency opinions and 8 addressed the field reliability of sanity opinions. These studies presented a wide range of reliability estimates; pairwise percentage agreements ranged from 57% to 100% and kappas ranged from .28 to 1.0. Meta-analytic combinations of reliability estimates obtained by independent evaluators returned estimates of κ = .49 (95% CI: .40-.58) for competency opinions and κ = .41 (95% CI: .29-.53) for sanity opinions. This wide range of reliability estimates underscores the extent to which different evaluation contexts tend to produce different reliability rates. Unfortunately, our study space analysis illustrates that available field reliability studies typically provide little information about contextual variables crucial to understanding their findings. Given these concerns, we offer suggestions for improving research on the field reliability of competency and sanity opinions, as well as suggestions for improving reliability rates themselves. (PsycINFO Database Record

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concerns about unreliability and bias in the forensic sciences. Two broad categories of problems also appear applicable to forensic psychology: (1) unknown or insufficient field reliability of forensic procedures, and (2) experts' lack of independence from those requesting their services. We overview and integrate research documenting sources of disagreement and bias in forensic psychology evaluations, including limited training and certification for forensic evaluators, unstandardized methods, individual evaluator differences, and adversarial allegiance. Unreliable opinions can result in arbitrary or unjust legal outcomes for forensic examinees, as well as diminish confidence in psychological expertise within the legal system. We present recommendations for translating these research findings into policy and practice reforms intended to improve reliability and reduce bias in forensic psychology. We also recommend avenues for future research to continue to monitor progress and suggest new reforms. What is the significance of this article for the general public?This review summarizes and integrates research on sources of disagreement and bias in forensic psychology evaluations, including limited training and certification, unstandardized methods, individual evaluator differences, and allegiance to the retaining party. Disagreement can result in arbitrary or unjust legal outcomes for forensic examinees, as well as diminish confidence in psychological expertise. Thus, policy and practice changes are needed to improve the reliability of forensic opinions.

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