Forensic Assessments of Alcohol, Cannabis and Methamphetamine Intoxication in Cases of Violent Offending.

Whether a person was voluntarily or intentionally intoxicated at the time of commission of a violent offence is a common question in forensic contexts. While a person who was intoxicated may not be able to form the requisite specific intent to commit some offences, voluntary intoxication usually disentitles a person from an insanity or "mental impairment" defence. However, a person may also consume alcohol or use a substance without becoming intoxicated and the presence of alcohol, substances or metabolites of substances in a person's urine or blood is not conclusive when the question of intoxication is relevant. A jury (or a judge sitting without a jury) may require expert opinion evidence when cannabis or methamphetamine intoxication are implicated in the alleged offending.