Alcohol tops the list of psychoactive substances encountered in police investigations of crimes such as mugging, murder, sexual assault, and especially impaired driving. Accordingly, the need often arises to interpret a person`s blood-alcohol concentration (BAC) in relation to the degree of alcohol influence and the amount of alcohol consumed. Such calculations are usually done with the aid of so-called “know your limit” or blood-alcohol charts, and more recently, several computer programs have been developed for this purpose.