How Psychology Expert Witnesses Can Impact Criminal & Civil Cases


How Psychology Expert Witnesses Can Benefit Criminal & Civil Cases

Because psychologists are trained in the study of the human mind and behavior, it’s no surprise that they can offer unique perspectives in legal proceedings. Whether they are used to testify about the mental state of a defendant or the psychological damages inflicted on a plaintiff, psychology expert witnesses can educate the fact finder on issues that are not readily discernible by other forms of evidence.

What Qualifies a Witness as an Expert in Psychology?

Psychology is a varied field that has many subspecialties ranging from forensics to counseling to cognitive behavioral therapy. Some psychologists work as health care providers and engage in the treatment of patients, while others conduct research and statistical analysis. Although deciding the ideal background for a witness will hinge on the particular subject about which they will testify, all expert psychologists should have the necessary educational requirements, typically either a master’s or doctorate degree  in the field. Postdoctoral residency programs, internships, and other clinical work are real-life experiences that most experts should possess before they take the stand to testify. Furthermore, it is important to ensure that a practicing psychologist possesses the requisite licenses and is in good standing within their jurisdiction of practice.

Psychology Expert Witnesses in Criminal Cases

There is no greater judged party in a courtroom than a criminal defendant. After all, the purpose of a criminal trial is to adjudicate a defendant’s guilt. In many instances, either explicitly or implicitly, psychological issues come into play. The most obvious situation occurs when a defendant directly puts his mental state as issue, by either by claiming that he is incompetent to stand trial or claiming he is not guilty by reason of insanity. During a competency hearing, psychology experts are tasked with determining whether a defendant can meaningfully participate in his defense. Although a judge makes the final determination as to competency, the decision is oftentimes reliant on the opinions of the expert witnesses.

Psychologist experts also play an indispensable role when a defendant raises an insanity defense. Some jurisdictions, such as the federal courts, prohibit psychologists from stating whether a defendant did or did not possess the requisite mental state to commit the crime, as such an opinion would be considered an issue reserved for the trier of fact. However, the experts may provide observational or diagnostic opinions as to the defendant’s behavior, which can directly inform the fact finder of the ultimate issue.

The standard of proving insanity in the legal context is different from a clinician’s, and varies throughout jurisdictions. Some states follow the M’Naghten test (whether a defendant understood the nature and consequences of his actions), while others look at whether the defendant was suffering from an irresistible impulse to engage in the criminal conduct. In either standard, a psychology expert witness can offer evidence in the form of data and studies in relation to the general issues, as well as observations and reports on the defendant specifically.

A psychology expert is not only helpful in the all-or-nothing, insanity defense context. A defendant who is deemed competent to stand trial and who may not be able to successfully argue an insanity defense can still raise mental health arguments that can affect the case’s outcome. A defendant may argue that he committed the offense while suffering from a significantly reduced mental capacity that substantially contributed to the commission of the offense. Likewise, at sentencing, evidence of a diminished mental capacity may also increase the defendant’s chances of receiving a more lenient sentence.

Psychology Expert Witnesses in Civil Cases

While incredibly important in criminal cases, psychology experts are also critical in the civil context as well. Damages related to psychological conditions, such as emotional distress and pain and suffering, are becoming quite common when assessing the compensatory damages amount due to a plaintiff. Sometimes, psychological injuries are longer lasting than the actual physical injuries (i.e., a car accident that resulted in the plaintiff suffering from post-traumatic stress). Although life-changing, a plaintiff’s psychological harm is not as easy to prove as a broken bone or laceration, which is why expert testimony is critical. Psychology experts can provide evaluations and offer opinions as to the emotional impact the incident may have had on the plaintiff. While experts cannot opine as to the awards amount, a psychologist can provide insight as to the plaintiff’s condition and how it will affect their day-to-day life both presently and in the future. From this information, a jury can more accurately glean a suitable damages amount.

Overall, psychology expert witnesses can offer an inner look into the minds of the parties, which can ultimately assist the trier of fact in coming to a decision. Whether in the criminal or civil context, a psychologist can help any case that hinges on the mental conditions of either the plaintiff or defendant.

About The Author

Anjelica Cappellino, J.D. is an accomplished defense attorney and legal writer who has represented numerous federal criminal defendants in the Southern and Eastern Districts of New York.