Although alcohol and drug use features prominently in many areas of criminal offending, there has been limited investigation of how the effects of alcohol and other drugs are treated by criminal laws and the criminal justice system. This article examines the framing of judicial inquiries about ''intoxication'' in criminal cases in Australia. It illustrates the diverse types of evidence that may (or may not) be available to judges and juries when faced with the task of determining whether a person was relevantly ''intoxicated.'' It shows that in the absence of legislative guidance on how the task should be approached, courts tend to assign only a relatively marginal role to medical and scientific expert evidence, and frame the question as one that can be answered by applying common knowledge about the effects of alcohol and other drugs. The article examines the adequacy of this approach, given the weak foundation for assuming that the relationship between intoxication and the complex cognitive processes on which tribunals of fact are often required to reach conclusions (such as intent formation) is within the lay knowledge held by jurors and judges.