Toxicology is the study of the adverse effects of drugs on the human body. In forensics, toxicology is applied to the legal system. Analysts identify various chemicals, including common street drugs, prescription medications, alcohol and other volatile substances in liquids or biological specimens. Analysts use scientific methods and highly sensitive instruments to determine the presence and quantity of alcohols and other drugs and extract them from the samples. The analysts also testify in court to explain their findings and the impact a particular drug can have on human performance and behavior.