Personality theory, as proposed by scholars and psychologists such as Freud, Erickson, Eysenck, Allport, and Maslow (among a myriad of others), entails that each individual possesses a number of inherent traits that manifest depending on different situations. The manner in which we allow certain traits to dominate a situation, and the way in which we choose to control a situation (or not) define who we are and what we are willing to do with our character traits.
The Diagnostic Statistics Manual -IV (DSM-IV) is the comprehensive text that offers all the psycho-pathological findings as far as bio-psychological, bio-social, and psychological/psychiatric conditions and illnesses. In a Law enforcement scenario, knowing whether a defendant has any of these conditions enables the following:
- avoiding a mistrial or overturning a verdict due to the defendant being mentally ill
- understanding the rationale behind a criminal's behavior
- predicting whether a defendant is or is not a danger to the community
- tracking and predicting behavioral patterns
- finding ways to address a criminally-insane defendant in a way that information can be obtained with ease
- predicting a criminal's "next move"
Since some personality types are manipulative and enthralling, an investigator must prepare himself for all kinds of trickery and lies during interrogation. This is why it is important to understand disorders such as
- histrionic personality disorder
- bipolar disorder and
- borderline personality disorder
Other personality changes occur as a result of stress, depression, and other environmental variables that have nothing to do with the accused. In fact, the accused may be innocent but still manifest traits that may self-incriminate him.
For this reason, a wise investigator would learn the difference between true pathology and mimicry, or plain psychosis caused by stress. This will result in more effective interviewing techniques and in higher chances of getting the right information about a case.