In cold blood: characteristics of criminal homicides as a function of psychopathy.

This study investigated the relationship between psychopathy and the characteristics of criminal homicides committed by a sample of 125 Canadian offenders. It was hypothesized that the homicides committed by psychopathic offenders would be more likely to be primarily instrumental (i.e., associated with premeditation, motivated by an external goal, and not preceded by a potent affective reaction) or "cold-blooded" in nature, whereas homicides committed by nonpsychopaths often would be "crimes of passion" associated with a high level of impulsivity/reactivity and emotionality. The results confirmed these predictions; homicides committed by psychopathic offenders were significantly more instrumental than homicides by nonpsychopaths. Nearly all (93.3%) of the homicides by psychopaths were primarily instrumental in nature compared with 48.4% of the homicides by nonpsychopaths.