Post-WWII Expansion of Forensic Psychology in the USA

Before World War II, psychology and the American legal system operated largely in separate spheres. Psychologists rarely appeared in courtrooms, and when they did, their credibility was often questioned. But the post-war period changed everything. A surge in professionalization, landmark legal cases, and a growing public awareness of mental health transformed forensic psychology from a niche interest into a recognized and essential discipline. The decades following WWII laid the groundwork for what forensic psychology is today – a field that is deeply embedded in the American justice system.

Why did WWII accelerate growth in forensic psychology? 🔗

World War II created an unprecedented demand for psychologists. The U.S. military needed professionals who could assess soldiers’ mental fitness, treat trauma, and evaluate personnel for various roles. This large-scale involvement gave psychologists practical, real-world experience and elevated the profession’s status in the eyes of the public and institutions alike. When the war ended, thousands of trained psychologists returned to civilian life, bringing with them new skills in assessment, testing, and clinical evaluation.

This post-war professionalization had a direct spillover effect on the legal system. Courts, law enforcement agencies, and correctional facilities began to see the value of psychological expertise. As iResearchNet’s history of forensic psychology notes, the rapid growth of mental health professions during this period, combined with the development of new legal doctrines around insanity and mental competence, created fertile ground for psychologists to enter the courtroom. Psychologists were no longer confined to laboratories or clinics – they were becoming active participants in the justice system.

People v. Hawthorne (1940): a turning point for expert testimony 🔗

One of the most important early milestones came just before the war. In People v. Hawthorne (1940), a Michigan case, the question of whether a psychologist could serve as an expert witness on mental illness was put to the test – and the outcome helped reshape the field.

What happened in the case? 🔗

William Hawthorne was charged with killing his wife’s lover and entered a plea of not guilty by reason of insanity. During the trial, the defense attempted to call a psychology professor from Michigan State Normal College as an expert witness on the question of Hawthorne’s sanity. This professor held a doctoral degree and had impressive academic credentials, but he was not a medical doctor. The trial court refused to qualify him as an expert, ruling that only physicians could testify on matters of insanity.

The Michigan Supreme Court’s ruling 🔗

The case was appealed, and the Michigan Supreme Court weighed in with a significant opinion. It ruled that the trial court had erred. The standard for determining whether someone qualifies as an expert witness, the court said, should not be whether the person holds a medical degree – it should be the extent of the witness’s knowledge. A concurring justice wrote that a psychologist who had intensively studied insanity and brain diseases could not be presumed less capable than a physician whose experience in that area was less focused.

This was a landmark moment. Before Hawthorne, the prevailing assumption in American courts was that only medical doctors could speak authoritatively about mental conditions. This case opened the door for psychologists to be recognized as legitimate experts in courtroom settings, setting a precedent that would be built upon in the coming decades.

Jenkins v. United States (1962): solidifying the precedent 🔗

While Hawthorne cracked the door open, it was Jenkins v. United States (1962) that pushed it wide. In this case, the U.S. Court of Appeals for the District of Columbia directly addressed whether psychologists could serve as expert witnesses on the issue of mental illness. Although the court was sharply divided, it ultimately ruled in favor of allowing psychologists to testify.

Following the Jenkins decision, federal courts and an increasing number of state courts began certifying psychologists as expert witnesses in both criminal and civil cases. This ruling remains one of the most frequently cited authorities supporting the role of psychologists in the courtroom. Together, Hawthorne and Jenkins established a legal foundation that made it possible for forensic psychology to grow as a profession.

Brown v. Board of Education (1954): psychology enters the Supreme Court 🔗

If People v. Hawthorne showed that psychologists could contribute to individual criminal cases, Brown v. Board of Education (1954) demonstrated that psychological research could influence the direction of an entire nation. This case is arguably the most significant moment in the relationship between psychology and American law.

The doll tests of Kenneth and Mamie Clark 🔗

In the 1940s, psychologists Kenneth and Mamie Clark designed a series of experiments to study how racial segregation affected Black children’s self-perception. Their method was deceptively simple: they presented Black children, aged three to seven, with four dolls that were identical except for skin color. The children were then asked which doll they preferred, which was “nice,” which looked “bad,” and which looked most like them.

The results were disturbing. A majority of the children preferred the white doll and attributed positive characteristics to it, while rejecting the Black doll. The Clarks concluded that segregation created a deep sense of inferiority in Black children, damaging their self-esteem. As Kenneth Clark later recounted, many children became visibly upset when asked to identify the doll that looked like them – they had already rejected it as “bad.”

How psychology shaped the ruling 🔗

When the NAACP prepared its legal challenge to school segregation, its lawyers – led by Thurgood Marshall – drew on the Clarks’ research. Kenneth Clark testified in multiple lower court cases leading up to the Supreme Court hearing, presenting evidence that segregation caused measurable psychological harm to children. He also helped draft a summary of the social science evidence supporting integration.

In its unanimous 1954 decision, the Supreme Court ruled that racially segregated public schools were inherently unequal and violated the Equal Protection Clause of the Fourteenth Amendment. The Court’s opinion referenced the Clarks’ research and other social science evidence, noting that separating Black children from others of similar age solely because of race generated feelings of inferiority that could affect their development in ways unlikely to ever be undone.

This was historic for psychology as a discipline. As a study published in American Psychologist described, Brown v. Board marked the first time psychological research was cited in a Supreme Court decision. Social science data were seen as essential to the Court’s reasoning. The case demonstrated that psychology was not just useful in evaluating individual defendants – it could shape national policy and advance civil rights.

The rise of psychologists in law enforcement and legal processes 🔗

The courtroom was not the only arena where forensic psychology expanded after WWII. Psychologists increasingly contributed to law enforcement operations as well. Police departments began using psychological assessments to screen candidates, evaluate officers involved in critical incidents, and develop criminal profiles. Correctional facilities also started relying on psychologists for risk assessments, treatment programs, and parole evaluations.

This expansion was driven by several factors. The war had demonstrated the value of psychological testing on a massive scale. The public was becoming more receptive to mental health concepts. And legal doctrines were evolving – courts were developing more nuanced approaches to questions of insanity, competency, and criminal responsibility, all of which required psychological expertise.

By the 1960s and 1970s, forensic psychology was growing rapidly across multiple fronts. Professional organizations began forming to support practitioners. The American Psychology-Law Society was founded in 1969, later becoming Division 41 of the American Psychological Association. The American Board of Forensic Psychology was chartered in 1976, offering board certification and establishing professional standards for the field.

APA’s formal recognition in 2001 🔗

Despite its decades of growth, forensic psychology did not receive formal recognition as a specialty from the American Psychological Association (APA) until 2001. This recognition was a watershed moment for the field. It meant that forensic psychology was no longer just an informal area of practice – it was an officially acknowledged specialty with its own standards, guidelines, and expectations for training.

What did APA recognition mean in practice? 🔗

The APA’s recognition initially focused on the clinical aspects of forensic work – assessment, treatment, and consultation within legal settings. But the field’s scope continued to broaden. The Specialty Guidelines for Forensic Psychologists, first adopted in 1991 and revised in 2011, reflected an expansive view of forensic psychology that included research, expert testimony, jury consultation, correctional work, and more.

The formal recognition also had major implications for education and training. Universities began offering dedicated graduate programs in forensic psychology, training students specifically for careers at the intersection of psychology and law. Doctoral programs, internships, and post-doctoral fellowships in forensic psychology became more widely available. The number of academic journals, textbooks, and conferences devoted to the field grew significantly.

Why did it take until 2001? 🔗

The delay partly reflected longstanding debates within psychology about what forensic psychology actually was. Some defined it narrowly – limited to clinical psychologists working directly in legal settings. Others saw it more broadly, including researchers studying jury behavior, eyewitness testimony, criminal profiling, and other topics. The APA’s 2001 recognition, and the subsequent broadening of the field’s definition, helped resolve this tension by embracing both clinical and research dimensions.

The legacy of post-WWII growth 🔗

The decades following World War II were transformative for forensic psychology in the United States. A few key developments stand out as defining this era:

People v. Hawthorne (1940) established that psychologists could serve as expert witnesses, challenging the long-held assumption that only physicians could speak to mental health matters in court. Brown v. Board of Education (1954) showed that psychological research could influence Supreme Court decisions and national policy, elevating the discipline’s prestige and relevance. Jenkins v. United States (1962) further solidified psychologists’ standing in the courtroom. And the APA’s formal recognition in 2001 gave the field institutional legitimacy, spurring growth in education, research, and professional practice.

Today, forensic psychologists serve in an extraordinary range of roles – from evaluating a defendant’s competency to stand trial, to consulting with law enforcement on criminal investigations, to conducting research on false confessions and eyewitness reliability. The field that barely existed in American courtrooms before WWII is now an indispensable part of the justice system.

What do you think? Considering how much forensic psychology has grown since the mid-20th century, do you believe courts rely enough on psychological expertise today – or do you think there are still areas of the legal system where psychology’s role should expand further?

References

1. https://psychology.iresearchnet.com/forensic-psychology/history-of-forensic-psychology/
2. https://criminal-justice.iresearchnet.com/forensic-psychology/history-of-forensic-psychology/expert-testimony/
3. https://en.wikipedia.org/wiki/Forensic_psychology
4. https://psychology.iresearchnet.com/forensic-psychology/history-of-forensic-psychology/history-of-expert-testimony/
5. https://www.naacpldf.org/brown-vs-board/significance-doll-test/
6. https://www.smithsonianmag.com/science-nature/psychologist-work-racial-identity-helped-overturn-school-segregation-180966934/
7. https://pubmed.ncbi.nlm.nih.gov/11885301/
8. https://www.forensicpsychologyedu.org/what-is-forensic-psychology/
9. https://ap-ls.org/resources/guidelines/introduction