Psychology Meets the Law: An Unlikely (and Complicated) Partnership

When psychology wanders into the courtroom, things get complicated. Psychology, at its core, thrives on nuance, ambiguity, and the exploration of human thought and behavior in all its contradictory forms. The law, by contrast, demands crisp categories, sharp lines, and definitive yes-or-no answers. The two do not always sit comfortably together. Forensic psychology has become an essential, if uneasy, partner in the pursuit of justice.

Forensic psychology is broader than popular culture often suggests. It is not limited to profilers chasing serial killers or dramatized television experts reconstructing motives. Instead, it encompasses the many ways psychological science informs the legal system. For example, developmental psychology contributes when courts must decide whether juveniles can be tried as adults, or when intellectual disabilities complicate assessments of culpability. Cognitive psychology steps in when evaluating memory, testimony, or a defendant’s competency to stand trial. Clinical psychology intersects with questions of mental illness, the insanity defense, and rehabilitation. Social psychology, meanwhile, examines jury behavior, eyewitness reliability, and the dynamics of courtroom persuasion. Forensic psychology does not sit in a silo. It cuts across the discipline, appearing whenever human behavior and legal decision-making collide.

A foundational distinction in this field is the difference between competency and insanity, concepts that are often confused by the public but are crucial in court. Competency refers to the present ability of a defendant to understand the charges and participate in their trial. If they cannot do so, they cannot legally be tried. Insanity, on the other hand, concerns a defendant’s mental state at the time of the crime. Was the individual, because of mental illness, unable to understand what they were doing or that it was wrong? The two questions often overlap but remain distinct. A person might have been legally insane during the crime but competent to stand trial months later, or vice versa. Famous insanity cases that reached trial did so precisely because defendants were found competent enough to face proceedings, which is one reason such stories dominated headlines.

Although forensic psychology may seem modern, its roots stretch back over a century. Sigmund Freud, perhaps unexpectedly, once testified in court about how psychology could inform criminal punishment. Hugo Münsterberg, a student of Wilhelm Wundt and later a Harvard professor, published On the Witness Stand in 1908, one of the earliest works to highlight the flaws in eyewitness testimony. Around the same time, the Brandeis Brief in Muller v. Oregon (1908) argued that courts should incorporate social science research into their reasoning, a revolutionary idea that opened the door for psychological expertise in law. Later, Kenneth and Mamie Clark’s famous “doll studies,” presented in Brown v. Board of Education (1954), demonstrated the psychological harm of segregation on children and helped the U.S. Supreme Court dismantle racial segregation in schools. By the 1960s, the field had become institutionalized with the creation of the American Psychology–Law Society, which eventually became Division 41 of the American Psychological Association. What began as occasional forays by individual psychologists into the legal system has since grown into a robust field with journals, graduate programs, and its own professional infrastructure.

Yet law and psychology remain philosophical frenemies. The law looks backward, grounding itself in precedent: what has been decided before should guide what is decided now. Psychology, by contrast, is oriented toward the future, revising old models as new evidence emerges. The law is adversarial, built around a contest between prosecution and defense. Science, in principle, is objective, seeking to produce findings that hold true regardless of who conducts the study. When psychologists enter courtrooms as expert witnesses, these differences come to the surface. Experts are meant to present neutral science, yet in practice they often appear biased toward whichever side hired them. Sometimes they genuinely are. The history of tobacco companies funding “independent” research that downplayed links between smoking and cancer is a cautionary tale about how easily science can be bent to serve legal or financial interests. Scientists, after all, are human too.

Beneath these philosophical differences lies the deeper question of why we punish at all. Legal theory identifies five traditional purposes of punishment. Retribution views punishment as deserved suffering: an eye for an eye. Deterrence treats punishment as a warning, meant to dissuade others from crime. Incapacitation aims to protect society by removing offenders, usually through imprisonment. Rehabilitation seeks to reform offenders so they may return to society as law-abiding citizens. Restoration emphasizes repairing harm done to victims and communities through restitution or reconciliation. Psychology intersects with each of these justifications. Cognitive psychology informs debates about fairness in retribution: can someone truly deserve punishment if their decision-making was impaired? Social psychology questions whether deterrence works as intended, pointing out, for example, that the death penalty has not been shown to reduce homicide rates. Clinical psychology develops rehabilitative programs, while trauma psychology supports restorative approaches by addressing the needs of victims.

The history of criminal justice is full of examples where psychology helped evaluate “common sense” interventions. In the 1980s and 1990s, American policymakers embraced “get tough” programs like Scared Straight, juvenile boot camps, and D.A.R.E. On the surface, these seemed promising. If you frightened teenagers by taking them to prisons or lectured them about drugs, surely, they would change course. Yet careful research told a different story. Meta-analyses found that Scared Straight programs often increased rates of reoffending among participants (Petrosino et al., 2013). D.A.R.E., despite its ubiquity in classrooms, showed little to no effect on drug use, and in some cases appeared to introduce children to drug terminology they would not otherwise have known (West & O’Neal, 2004). Boot camps and “super-predator” rhetoric have since been debunked as moral panics rather than evidence-based solutions (Mears & Travis, 2004). Psychology’s role here was to test assumptions, revealing that catchy political slogans often fail to produce meaningful results.

In more constructive ways, psychologists now influence law through multiple channels. Expert witnesses testify about issues ranging from competency and insanity to eyewitness reliability and risk assessment. Attorneys sometimes consult psychologists during jury selection, seeking to understand potential biases. Psychologists contribute amicus briefs, or “friend of the court” documents, providing scientific expertise in appellate cases on topics such as juvenile sentencing or eyewitness identification. Researchers consult with legislators drafting policies on mental health or capital punishment. And across the system, psychologists evaluate whether programs, from rehabilitation initiatives to sentencing policies, are effective, ethical, or counterproductive. Each of these roles highlights both the promise and the challenge of translating nuanced psychological data into legal settings that often demand unambiguous answers.

At the center of this work lies an ethical tightrope. Forensic psychology is not clinical psychology, and confusing the two can have profound consequences. In a therapeutic setting, confidentiality is nearly absolute: what a client tells their therapist remains private, except under rare conditions involving imminent harm. In forensic settings, confidentiality often does not exist. The psychologist’s client is not the defendant but the legal system itself, meaning that anything revealed during an evaluation may be included in a report to the court. Similarly, the purpose differs. Clinical psychology seeks to heal; forensic psychology seeks to answer legal questions. Forensic evaluators must make this distinction clear from the outset, so that defendants do not mistake evaluators for therapists.

These complexities matter because the law touches everyone. Even those who never testify in court, serve on juries, or face criminal charges live in societies shaped by the justice system. Policies around policing, sentencing, mental health care, and victim advocacy are all informed, directly or indirectly, by the evolving dialogue between psychology and law. If the law is going to make decisions about people (and it always does) it cannot afford to ignore the science of people. Psychology provides tools for making justice more accurate, more humane, and fairer. The challenge, and the opportunity, lies in bridging the gap between a science comfortable with gray areas and a legal system that prefers sharp black-and-white divisions.

That is the task of forensic psychology: to straddle these two worlds, awkwardly at times, but always with the aim of making justice just a little smarter.

References

Mears, D. P., & Travis, J. (2004). Youth development and reentry. Youth Violence and Juvenile Justice, 2(1), 3–20. https://doi.org/10.1177/1541204003260044

Petrosino, A., Turpin-Petrosino, C., Hollis-Peel, M. E., & Lavenberg, J. G. (2013). ‘Scared Straight’ and other juvenile awareness programs for preventing juvenile delinquency: A systematic review. Campbell Systematic Reviews, 9(1), 1–55. https://doi.org/10.4073/csr.2013.5

West, S. L., & O’Neal, K. K. (2004). Project D.A.R.E. outcome effectiveness revisited. American Journal of Public Health, 94(6), 1027–1029. https://doi.org/10.2105/ajph.94.6.1027