An informant is a person who furnishes useful material about illegal activities to law enforcement and other agencies. Law enforcement agents may plant informants or recruit people from within a criminal organization or community to become sources, depending on the situation and their needs. In exchange for providing information, this person receives immunity from prosecution for any activities he engages in while working for law enforcement, and may receive leniency for prior crimes as well. Related is the jailhouse informant, a person who talks to law enforcement or attorneys about other prisoners in the hopes of a reduced sentence.
The practice of using informants is ancient, and sometimes controversial. Law enforcement organizations rely on sources of internal information for major investigations. Often, insiders can allow officers to cast a wider net, catching people at the head of a criminal organization, as well as street-level operatives. Drug kingpins, for example, rarely deal on street corners. Prosecuting street dealers will not resolve a drug problem, while finding and jailing the head of the organization cuts off the head of the hydra, creating chaos and disorganization.
Some informants are undercover law enforcement officers who go into “deep cover” with an organization. They collect information by participating in daily activities and playing a role as a member. When they have enough material, a law enforcement bust can occur, with uniformed officers arresting members of the group and allowing the undercover officer to return to normal duty. Other informants are recruits from within an organization. Law enforcement, working with a district attorney, can promise leniency for people if they agree to return to an organization and convey knowledge about it to the police.
A confidential informant will have a handler who periodically arranges a meeting to debrief and collect data. These meetings are kept irregular to avoid attracting attention. Once the investigation is over, the informant may receive protection from reprisals in addition to forgiveness for criminal activities. In addition to using people to investigate clearly illegal activity like drug dealing and organized crime, law enforcement may also rely on informants to collect material about activist organizations, churches, and other groups which may not necessarily be doing anything illegal.
In a jail setting, the jailhouse informant may provide information about people with the goal of receiving credit for this at parole and sentencing hearings. These informants are not very reliable sources, as they have a clear incentive to provide anything they can, including false material.