Screening out cases which do not merit criminal prosecution goes on from the moment a crime first comes to the attention of a government official (usually the police) to the time someone (usually the prosecutor) makes a decision to file a formal accusation in a court of appropriate jurisdiction. In the United States, for example, the police may decide not to arrest a suspect, even when they have sufficient evidence to do so. 1 Prosecutors, in their almost boundless discretion, may decide not to prosecute, or to withhold prosecution while the accused submits voluntarily to a diversion treatment program or informal probation. Magistrates (usually judges of lower criminal courts of limited jurisdiction) may decide at preliminary hearings or grand jurors at a grand jury hearing that the prosecutor has not adduced sufficient credible evidence to justify prosecution. 2 The definition of screening should also be extended to include decisions other than those not to arrest or prosecute, such as decisions to settle the case by trading possible criminal charges or penalty recommendations for the accused's agreement not to contest the prosecution or to enter a plea of guilty. Even though such agreements do not avoid the formalities of accusation and prosecution, they do eliminate or abbreviate later stages of the proceeding, such as trial and appeal, and, like other screening procedures, reduce the administrative burdens on the system.
Screening practices may or may not be regulated by legal rules of