Informant
From ArticleWorld
An Informant is generally known as a person who gives information to courts and other authorities in exchange for getting themselves released from prison or to get themselves some benefit including a reduced sentence or even reducing the ability of authorities to charge them with a certain crime.
Most commonly found among members of organized crime, informants generally are people involved in illegal activity of some type. Perhaps the reason that informants are common among organized crime is that participants in illegal activities are acutely aware of the guilt of the other people involved in the crime they are committing.
A related area, where illegal activities are commonplace is drug trade. Often times, drug lords are released from prison after they serve officials as an informant. The CIA has come under fire in recent years for releasing these criminals.
The role of an informant to an investigation usually happens when officials require the informant to participate in the same illegal activity about which they are providing information. There are ethical questions about whether is it right to allow criminals to repeat their offenses.
Generally, it is uncommon for a person to serve as an informant in any form until they themselves have been arrested or charged with a crime. An exception of this is terrorist organizations, where people tend to become informants in order to remove themselves from the organization completely.
Other terms used for informants include snitch and rat. The slang terms are much more commonly used by the public. Oddly, the word grass is slang for an informant in the U.K..
Other Definitions
Informant, to those studying linguistics refers to people who speak a certain dialect of a particular language and share information about the structure and grammar used in their language.