Criminal Justice

Impulsive murderers more likely to be cognitively impaired than premeditated murderers, study finds

The minds of murderers who kill impulsively, sometimes out of rage, differ from those of premeditated murderers who plan their crimes, according to a Northwestern Medicine neuropsychologist.

Researcher Robert Hanlon administered intelligence and neuropsychological tests to 77 convicted murderers in Illinois and Missouri. A Northwestern University press release highlights his findings:

• Compared to predatory murderers, impulsive murderers are more likely to be developmentally disabled and have cognitive and intellectual impairments—59 percent versus 36 percent.

• Compared to impulsive murderers, premeditated murderers are almost twice as likely to have a history of mood disorders or psychotic disorders—61 percent versus 34 percent.

• Ninety-three percent of the impulsive murderers had a history of alcohol or drug abuse, or were intoxicated at the time of the crime, compared to 76 percent of the premeditated murderers.

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