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Psychological Tests Used In Court Are Often ‘Junk Science’

New research suggests courts often admit psychological tests as evidence that are not scientifically valid. Yet they can play a role in determining parental fitness for child custody, assessing the sanity or insanity of a person at the time of a crime, and judging eligibility for capital punishment.

Once introduced into a case psychological instruments are rarely challenged, according to Dr. Tess Neal, an assistant professor of psychology at Arizona State University.

“Given the stakes involved one would think the validity of such tests would always be sound,” Neal said. “But we found widespread variability in the underlying scientific validity of these tests.”

The problem is made worse because the courts are not separating the good from the bad.

“Even though courts are required to screen out ‘junk science,’ nearly all psychological assessment evidence is admitted into court without even being screened,” Neal said.

Neal presented her findings at the annual meeting of the American Association for the Advancement of Science in Seattle.

In a two-part investigation, Neal and her colleagues found a varying degree of scientific validity to 364 commonly used psychological assessment tools employed in legal cases. The researchers looked at 22 surveys of experienced forensic mental health practitioners to find which tools are used in court.

With the help of 30 graduate students and postdocs, they examined the scientific foundations of the tools, focusing on legal standards and scientific and psychometric theory. The second part of the study was a legal analysis of admissibility challenges with regard to psychological assessments, focusing on legal cases from across all state and federal courts in the U.S. for a three-year period (2016-2018).

“Most of these tools are empirically tested (90 percent), but we could only clearly identify two-thirds of them being generally accepted in the field and only about 40 percent as having generally favorable reviews of their psychometric and technical properties in authorities like the Mental Measurements Yearbook,” Neal explained.

“Courts are required to screen out the ‘junk science,’ but rulings regarding psychological assessment evidence are rare. Their admissibility is only challenged in a fraction of cases (5.1 percent),” Neal said.

“When challenges are raised, they succeed only about a third of the time. Challenges to the most scientifically suspect tools are almost nonexistent,” Neal added. “Attorneys rarely challenge psychological expert assessment evidence, and when they do, judges often fail to exercise the scrutiny required by law.”

According to researchers, what is needed is a different approach.

In an open-access paper in Psychological Science in the Public Interest, Neal and her colleagues offer concrete advice for solving these problems to professionals and the public. Professions targeted include psychological scientists, mental health practitioners, lawyers, judges and members of the public interacting with psychologists in the legal system.

“We suggest that before using a psychological test in a legal setting, psychologists ensure its psychometric and context-relevant validation studies have survived scientific peer review through an academic journal, ideally before publication in a manual,” Neal explained.

“For lawyers and judges, the methods of psychologist expert witnesses can and should be scrutinized, and we give specific suggestions for how to do so.”

Source: Arizona State University/EurekAlert

Psychological Tests Used In Court Are Often ‘Junk Science’

Rick Nauert PhD

Rick Nauert, PhDDr. Rick Nauert has over 25 years experience in clinical, administrative and academic healthcare. He is currently an associate professor for Rocky Mountain University of Health Professionals doctoral program in health promotion and wellness. Dr. Nauert began his career as a clinical physical therapist and served as a regional manager for a publicly traded multidisciplinary rehabilitation agency for 12 years. He has masters degrees in health-fitness management and healthcare administration and a doctoral degree from The University of Texas at Austin focused on health care informatics, health administration, health education and health policy. His research efforts included the area of telehealth with a specialty in disease management.

APA Reference
Nauert PhD, R. (2020). Psychological Tests Used In Court Are Often ‘Junk Science’. Psych Central. Retrieved on November 23, 2020, from
Scientifically Reviewed
Last updated: 18 Feb 2020 (Originally: 18 Feb 2020)
Last reviewed: By a member of our scientific advisory board on 18 Feb 2020
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