One of the common investigative actions depicted in crime shows is the lineup. The suspect and four or five other guys are displayed on a stage so the victim or witness, safely ensconced behind a two-way mirror, can make a positive identification.
"Live" lineups are rare in real police work because of the difficulty in setting them up. Finding four or five bodies of the same size and build of the suspect can be a challenge. Since live lineups are generally used when the suspect is already in custody, other jail inmates are used to fill out the lineup. Because of the time it takes to organize a live lineup, they are used primarily in serious crimes--rape, robbery, murder. More times than not, the suspect has a previous record so mug shots are usually available to prepare a photographic lineup.
To create a live lineup, other inmates in the jail can be asked to appear in the lineup. Normally that requires adding a little compensation to their commissary account in return for their participation. Inmates who were already incarcerated at the time of the offense are used to guarantee a misidentification isn't going to cause them any problems. In a rural community with a small jail, there may not be sufficient persons available to fill out a lineup.
The lineup is arranged by the case detective with help from the jail staff. Sometimes an assistant D.A. may be involved. If the suspect has already made a court appearance, his defense attorney must be invited to attend to observe but he or she can not participate or interfere in the process in any way. There is no requirement that a defense attorney be given access to a photographic lineup.
For the lineup, a detective would escort the victim/witness to the jail, preferably to a viewing room where the inmates & suspect can not see. The lineup of individuals is photographed for use in court. Of course, you can use the photographs to take the lineup to a witness if for some reason you don't want to use a live lineup.
A "showup" occurs when a potential suspect is located near the scene of a crime shortly after it occurs. The victim or witness is taken to the spot where the suspect has been stopped and makes a determination if that is the person who committed the crime. Showups are suggestive by nature so caution is advised in their use.
The common photo lineup, called a "six pack" in some locales, consists of pictures of the suspect and five other similar "fillers." Here's a typical photo lineup:
Many police agencies are now going to sequential photo lineups. Rather than showing the witness six suspects where they might pick out the one who most resembles the perpetrator, this method purportedly reduces the chance of an incorrect identification. The witness is shown a batch of photos sequentially--one at a time--rather than simultaneously. Some states have passed laws requiring this method.
The photo lineup doesn't provide exciting TV drama. The live lineup provides opportunity for confrontation, an emotional response from victims, and a small victory for the police when their investigation has been strengthened by a positive ID. But by far, most suspect identifications are verified by photographs, not face-to-face confrontations.