Relator

A relator refers to a specific person who has assisted the court by transferring the hidden facts that are required for a successful prosecution.

Additional Sources

Answers.com

A beneficially interested person on whose behalf an action is maintained by a sovereign power or a state.

Duhaime Legal Dictionary

An informer; a person who has supplied the facts required for a criminal prosecution or a civil suit.

Lawyers.com

A party other than the plaintiff upon whose information, knowledge, or relation of facts an action is brought when the right to bring the action is vested in another.

The Free (Legal) Dictionary

The individual in whose name a legal action is brought by a state; the individual who relates the facts on which an action is based.