Forensic Psychology

Forensic psychology is a term used to describe a broad and growing range of research topics and applications that address human behavior in the legal system. Forensic psychologists participate as scientists, trial consultants, advocates, critics, expert witnesses, and policy advisers. In so doing, they work not only in research laboratories and mental health clinics but also in police stations, courtrooms, prisons, juvenile detention facilities, and other legal settings.

Although there is a great deal of overlap, there are two types of forensic psychologists: research scientists and clinical practitioners. Trained in the principles and methods of basic psychology, forensic researchers study a wide range of issues, such as group dynamics as it applies to how juries deliberate and make decisions; the processes of perception and memory as they influence eyewitness identifications and testimony; the processes of persuasion as they apply to police interrogations and the confessions they produce; cognitive development as it applies to the testimony, accuracy, and suggestibility of children; personality testing as it applies to the criminal profiling of serial bombers, rapists, arsonists, and other types of offenders; and the use of the polygraph and other measures of bodily arousal for use as lie detector tests.

Clinically oriented forensic psychologists are mental health professionals trained primarily in assessment, diagnosis, treatment, and counseling. Working in criminal, civil, and family law, they are involved not only in conducting research but in making important judgments in specific cases, such as whether offenders were legally responsible or insane while committing their crime; whether defendants are competent or incompetent to stand trial; whether prisoners are dangerous psychopaths or worthy of release on parole; whether a parent is fit to have custody of a child; whether young children have been physically or sexually abused; whether victims of rape have suffered trauma, making it difficult for them to come forward; and whether plaintiffs in civil lawsuits have [Page 357]suffered emotionally as a result of an accident, injury, discrimination, or harassment.

Three problems illustrate what forensic psychologists do and how their work is used in the legal system. The first concerns the limits of eyewitness memory. As a result of recent advances in DNA technology, it is now possible to match suspects to samples of blood, hair, saliva, or semen found at a crime scene, enabling authorities to both identify criminals and absolve the innocent. Many prisoners have thus been exonerated, or found innocent, of the crimes for which they were convicted. Astonishingly, these cases reveal that eyewitness memory errors are by far the most common problem, appearing in three out of four DNA exonerations.

What factors diminish an eyewitness's memory, and can it be improved? Over the years, researchers have identified a number of problems. For example, research shows that people find it more difficult to recognize members of a race other than their own; that the sight of a weapon reduces a witness's ability to identify the perpetrator; that witnesses tend to pick from a lineup any person who stands out relative to the others. Making it doubly difficult for juries, research shows that eyewitnesses often report being highly confident in their memories, even when mistaken. To improve eyewitness performance, the U.S. Justice Department in 1999 published a set of research-based guidelines for police. Among the recommended methods were that police should ask questions that are open-ended rather than leading; that police should present witnesses with lineups that contain a single suspect and at least five others who generally fit the witness's description; and that witnesses should be instructed that the perpetrator may or not be presented in the lineup. Helping to improve eyewitness performance in these ways, forensic psychologists who study social influences on human perception and memory play a valuable role in the legal system.

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