Violence is unfortunately a part of society. The causes of violence are not completely understood, but it involves sociological, genetic, financial, biological, and environmental factors. Drugs can cause aggression by altering the neurotransmitters dopamine, norepinephrine, gamma-aminobutyric acid (GABA), and serotonin. Specific drugs associated with aggression include alcohol, anabolic steroids, cocaine, amphetamines, sedatives, opiates, and hallucinogens. Aggression can be categorized into impulsive and predatory aggression. Drugs under certain conditions cause impulsive aggression. Sometimes a defense in criminal cases is that the drug caused the violence, that is drug-induced insanity. A case of insanity is more likely to be accepted if the event was unplanned and had no apparent motive. An acceptance of insanity by voluntary intoxication is rarely accepted by the criminal justice system. A more common legal strategy is to seek diminished capacity which aims to obtain a reduction in the severity of the criminal charges. The author will discuss some, but not all of the pharmacological and physiological issues relating to drug-induced violence. Then some of the "big picture" forensic issues will be presented. The goal is to present a primer on the pharmacological and forensic issues relating to drug-induced violence. No attempt was made to provide a comprehensive review of all the literature related to drug-induced violence. (Published Abstract)