Crime Library: Criminal Minds and Methods

Multiple Personalities: Crime and Defense

Deception Detection

One idea about lying is that it is a more complicated activity than truth-telling and thus produces certain physiological reactions, such as a heightened pulse rate, dilated pupils, and certain behavioral manifestations. This is especially true if the stakes are high, such as going to prison. However, people telling the truth under conditions like that may also display emotion. They may be anxious about whether they are believed or may be embarrassed to be there under those conditions. To further complicate the problem, psychopaths and pathological liars are very good at lying and their skill makes the typical modes of detection irrelevant. They appear to have lower levels of autonomic nervous activity and are not as adversely affected by the idea of punishment.

In general, the conditions under which people tend to be apprehensive about lying include when the target person has a reputation for reading lies, when the target person is suspicious, when the deceiver has little experience lying, and when the consequences of being found out are serious.

The types of behaviors that may signal deception include narratives with more negative than positive statements, overgeneralizations, and deflections; uninterrupted talking with slower speech rate; speech hesitations and pauses; certain shifts in the body or unnecessary blinking; and an increase in nervous habits.

None of these is definitive, but these indicators tend to show up more often in those with the greatest motivation to deceive. However, those people who appear to be the best liars under pressure have experience with lying (probably have lied since childhood, are comfortable with attention, and are confident).

Malingering is a deliberate attempt to create the impression of being mentally ill, and in this context, it's often done to avoid a charge of criminal responsibility. To detect malingering of psychiatric symptoms, one may look for one of more of the following:

  1. an exaggerated presentation
  2. inconsistent information
  3. a deliberateness of manner
  4. an attempt to display obvious (and stereotypical) symptoms
  5. an inconsistency with past psychiatric diagnoses of the same person

The clinician may check the defendant's past history of psychiatric confinement (if any) and any statements from witnesses (friends, family, prison guards, hospital staff) as to the person's condition, current and past. She may also have to observe the subject in various settings over a period of time. Key to an assessment will be discrepancies in the person's ability to focus and talk rationally with other people.

Maligners make a point of ensuring people pay attention to their illness, while most truly mentally ill people would rather not be the focus of attention. If the person says the delusions or hallucinations were sudden, this is inconsistent with the clinical picture of mental illness, except for drug-induced psychosis.

  • Malingering DID, as happened in Primal Fear, is a popular ploy. Those who work with DID patients should be on the lookout for:
  • Defendants who have a hard time retaining the voice and personality of the alter they blame for their crime.
  • Defendants who appear not to be confused by the criminal behavior, as would be likely in an authentic case.
  • Lack of evidence of a history of the kind of fragmenting and amnesia characteristic of MPD/DID in the defendant's background.

While those who fake it may get away with it, some psychiatrists are attempting to pinpoint the condition to a neurological disorder, and thus to be able to furnish the courts with physical proof.

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