The neurologist’s role in understanding violence and brain damage as a neurological defense of violent crime are reviewed by neurologists at Georgetown University, Washington, DC. Pincus stresses the role of biological factors as contributory to aggressive behavior and notes that cognitive impairment, lapses of attention, and psychotic symptoms are more common among violent compared to nonviolent criminals. He concludes that programs of research targeting brain damage and child abuse as causes of violence might lead to more effective preventive methods of management than prison expansion. Resnak points out that the majority of violent criminals have no history or evidence of brain damage and concludes that neurology will not solve the mystery of violent behavior and murder. Admitting that many murderers have a higher incidence of epilepsy, head injury, child abuse, malnutrition, and learning disabilities, but the majority of epileptics, abused, and mentally retarded do not commit violence. Both experts agree that brain damage can decrease the threshold for violent, impulsive behavior, and serve as a mitigating factor in determining responsibility and defense for some crimes. [1, 2]
COMMENT. Three criteria are required by law for alleged brain damage to serve as a mitigating factor in determining responsibility. 1) Is there evidence of brain damage (deviation from normal brain structure) and is it reponsible for a deficit (impairment or loss or alteration of intelligence and emotion, and behavioral abnormality)?; 2) Is the deficit a contributing cause of the defendant’s crime?; 3) Without the deficit and resulting behavior, would the crime not have happened? Of 14 death row juveniles who had committed capital crimes, 11 had suffered head trauma, 9 had abnormal EEGs or neurologic examinations, and 12 gave a history of physical or sexual abuse . Brain damage may unleash violence, but it does not explain it, according to Hachinski V. 
A study of frontal lobe-subcortical circuits in the mediation of a wide range of human behavioral disorders, reported from the Departments of Neurology, Psychiatry and Biobehavioral Sciences, UCLA School of Medicine, Los Angeles, CA  demonstrates that we should not entirely dismiss a possible role of brain damage in crimes of violence.