Psychology, Forensic

History of the Discipline

The field of forensic psychology first earned notoriety in 1843, following the attempted assassination of then British prime minister Robert Peel. Daniel M'Naghten, a shopkeeper from Glasgow, Scotland, mistakenly shot and killed the prime minister's secretary, Edward Drummond. Represented by four barristers (attorneys), the defense strategy relied on the testimony of nine medical experts, all of whom testified that M'Naghten was insane or partially insane. The medical testimony was not refuted, as the prosecution withdrew its case against the defendant. In what was perhaps the quickest verdict ever rendered, the jury found M'Naghten not guilty by reason of insanity, after only two minutes of deliberation.

Outraged by the verdict, Queen Victoria, who had been shot by a would-be assassin just three years prior to the M'Naghten incident, insisted that the matter be reviewed by the House of Lords. The result was the M'Naghten Rule, which states that in order for a criminal insanity defense to be successful, attorneys for the accused must clearly show that the defendant lacked the capacity to understand what he or she did and lacked an appreciation for its wrongfulness. This very standard is still used in nearly half of the state jurisdictions in the United States.

With the dawn of the twentieth century, the discipline of psychology emerged, and several notable practitioners made its applicability to the law and to legal decision making readily apparent. Sigmund Freud maintained that the word association method developed through psychoanalysis could aid fact finders, such as judges or jurors, in uncovering the guilt or innocence of a particular defendant. By carefully selecting key words or phrases related to a particular case, the psychologist would then instruct the defendant to respond with the first thought that came to his or her mind. In relation to the law, Freud described these techniques as “detective devices” that enabled therapists to uncover the “hidden psychical [unconscious] material” concerning a crime and the defendant's involvement in it (Freud [1906] 1959: 103).

Hugo Münsterberg, a Harvard University professor, also argued that applied psychology had much to offer the legal system. He claimed that the law could benefit from the principles and methods of psychology, especially as litigators assessed the perceptions and attitudes of witnesses, defendants, and jurors. Neither Freud nor Munsterberg was particularly successful in persuading the legal profession to accept the forensic possibilities psychology could offer practicing attorneys.

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