Psychology -- the study of human behavior -- intersects with the legal system in the specialty called forensic psychology. As with conventional psychology, the field is broad. Forensic psychologists might advise on jury selection, conduct research, evaluate and treat criminal offenders, or counsel law enforcement personnel and their spouses.

A Little History

Forensic psychology has its roots in research on witness testimony, according to the Psych Central website. In the late 1800s and early 1900s, psychologists began to study issues such as whether emotion affected eyewitness testimony and whether adults provided different testimony than children when both witnessed the same event. Other research issues revolved around the accuracy of testimony and whether the witness’ confidence in the answer indicated the accuracy of the answer. This was also the period when psychologists first began to offer expert testimony in court cases.

Reverse Recall

When people testify about an event such as a crime, they are likely to confabulate -- make up a story to fit the incomplete facts they have about an incident -- according to a September 2011 article in “The Economist.” For example, a witness might see a dark dog but initially be unsure of its color. In retelling the incident to a police officer, the witness will choose a color such as brown or black. This is normal behavior rather than an attempt to deceive, according to forensic psychologists. Researchers trying to improve witness recall have tried techniques such as presenting testimony in reverse order in the hope that it would decrease confabulation. Reverse recall, however, actually led to fewer correct observations by eyewitnesses.

Professional Certification

Forensic psychologists can become certified in their specialty through the American Board of Professional Psychology. Certification is not required for practice, however. To become certified, a psychologist must have 100 hours of education; supervised practice in forensic psychology; or at least 1,000 hours of experience in the field. A psychologist must have a doctoral degree in psychology and be licensed as a psychologist to sit for the certification examination, which involves a three-hour oral examination by three psychologists who hold the credential of Diplomate of Forensic Psychology.

Specialties and Forensics

Most forensic psychologists are clinical or counseling psychologists. A doctoral degree is required for both types of psychologists, along with a one-year internship, according to the U.S. Bureau of Labor Statistics. The psychologist must also have one to two years of professional experience and pass the Examination for Professional Practice in Psychology to become licensed, according to the BLS. Clinical and counseling psychologists must be licensed in all states.