In common law, a writ of qui tam is a writ whereby a private individual who assists a prosecution can receive all or part of any penalty imposed. Its name is an abbreviation of the Latin phrase qui tam pro domino rege quam pro se ipso in hac parte sequitur, meaning "(he) who sues in this matter for the king as well as for himself. ''
the qui tam provision of the false claims act
a writ whereby a private individual who assists a prosecution can receive all or part of any penalty imposed