Saliva testing has attracted great interest in the forensic scientific landscape recently, especially among institutions or legal authorities interested in determining drug concentrations (for application in the workplace, drug driving, legal issues associated with drug testing, and pharmacokinetics of selected drugs). Indeed, it has been established that oral fluid is an adequate alternative biological matrix to blood for the determination of xenobiotics and/or drugs of abuse and/or metabolites both in living and deceased individuals. The concentration of a detectable substance in saliva is generally proportional to the free fraction of the drug present in plasma; this measurement therefore makes it possible to correlate the concentration of the substance and its pharmacological effects on the individual. The purpose of this chapter is to examine the main analytical techniques developed thus far in saliva drug testing, from screening to confirmatory analysis, taking into account the interpretation of cut-off levels. Both well-defined and potentially problematic issues are highlighted from medico-legal and toxicological perspectives
