Informer
INFORMER, in a general sense, one who communicates information. The term is applied to a person who prosecutes in any of the courts of law those who break any law or penal statute. Such a person is called a common informer when he furnishes evidence on criminal trials or prosecutes for breaches of penal laws solely for the purpose of obtaining the penalty recovered, or a share of it. An action by a common informer is termed a popular or qui lam action, because it is brought by a person qui lam pro domino rege quam pro se ipso sequilur. A suit by an informer must be brought within a year of the offence, unless a specific time is prescribed by the statute. The term informer is also used of an accomplice in crime who turns what is called " king's evidence " (see ACCOMPLICE). In Scotland, informer is the term applied to the party who. in criminal proceedings, sets the lord advocate in motion.
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)
