Determining whether an individual is or is not using a specific drug is a key step in reducing the public health risks associated with illicit drug use; further, this determination can also have legal implications. There [Page 523]are three common ways of acquiring this information. The first method is to ask the person directly, that is, to elicit a self-report of his or her behavior. The second method is to perform biochemical analysis of bodily fluids or tissues. The third method is to ask a collateral (e.g., spouse or other relative, social worker, or probation officer) who may have knowledge.