Psychological Assessment of Diminished Capacity

Diminished capacity exists when a defendant has a mental disease or disorder which affects his/her state of mind, as it relates to the commission of a crime. Many crimes require that the person "knowingly or purposely" performs some act.  If a psychological disorder interferes with knowing or purposeful behavior, then this evidence can be presented to the jury for consideration in determining guilt or innocence.

 A federal appeals court has ruled that if the evidence of mental disease or defect creates a reasonable doubt about a required mental state, the defendant must be acquitted of the charges. Thus, the burden of proof in establishing diminished capacity, is if the presence of a psychological disorder suggests that there is reasonable doubt concerning the required state of mind, then the defendant must be acquitted.  However, this is not the same as an insanity defense, as the person can still be found guilty of a lesser charge that does not require a specific mental state.

The New Jersey Supreme Court has found that any or all mental disorders can satisfy the requirements of a diminished capacity defense ( in terms of having a mental disorder).  So, psychologists may be asked to evaluate a defendant to determine whether he/she has a mental disorder, and further, whether that mental disorder could have impaired his/her capacity to knowingly or purposely commit a criminal act.

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