An eyewitness identification of a person, place, or object may occur through a direct one-on-one examination of the person, place, or object (showup); viewing of a photographic array (photo lineup); or the viewing of a group of persons (lineup). The due process clause of the 14th amendment of the U.S. Constitution protects defendants against an unnecessarily suggestive eyewitness identification. Courts will invalidate an in-court eyewitness identification when it follows a pretrial identification procedure that was "so impermissibly suggestive as to give rise to a very substantial likelihood of irreparable misidentification." Reliability is the linchpin in determining the admissibility of identification testimony. Reliability may be assessed by examining such factors as the opportunity of the witness to view the offender at the time of the crime, the witness' degree of attention, the accuracy of the witness' prior description of the offender, the degree of certainty shown by the witness at the confrontation, and the length of time between the crime and the confrontation. The court cases reviewed pertain to the legality of various eyewitness identification procedures.