The threat of international terrorism and the runaway growth of illicit drug trafficking over the past 20 years have forced law enforcement agencies to expand their use of informants to unprecedented levels. An informant is generally someone who has contacted the criminal justice system because of a criminal lifestyle, but is granted immunity from appropriate criminal justice sanctions in return for giving the police information about persons in the criminal underworld or participating with undercover police in illicit drug transactions that produce arrests of the unwitting participants. Although in theory the police maintain that informants are not made immune from prosecution should they break the law in the course of their informant career, in practice, much of the lawbreaking of the informant is overlooked in the interest of maintaining him/her as a valuable information source. Informants will often continue as drug users and even pushers, with their immunity from prosecution being rationalized as necessary to establish their credibility in the drug network. Further, the informant is free to supply or withhold information from the police to serve his/her own interests in the illicit drug network, so that enemies are given over to the police, while the informant's own network of profit or drug use is protected. The expansion of the informant system not only maintains a growing number of criminals in the criminal underworld and outside rehabilitative influences, but also increases a system whereby citizens' privacy is more easily invaded by and the police become increasingly involved in creating the scenarios of criminal behavior.