A chronology for the discrete stages of a criminal prosecution may be identified in the criminal procedure systems of all jurisdictions. Traditionally, prosecutors have the authority at each stage to choose not to move forward to the next stage. After the initiation of “adversary judicial proceedings,” indigent defendants are entitled to the assistance of appointed counsel under the federal constitution at “critical stages” of the prosecution.
Police officers obtain information about criminal activity from their own observations and/or other sources, including such informants as eyewitnesses, victims, individuals engaged in criminal activity, and other persons in possession of hearsay information.
The investigation is conducted in order to determine whether a crime was committed and whether there is sufficient evidence that points to the guilt of a particular person. During this stage, police may employ such procedures as non-custodial questioning of suspects, witness interviews, various warrantless searches that do not require probable cause, and identification procedures such as lineups, showups, and photo arrays.