In the case of State of New Jersey versus Larry Henderson, the New Jersey Supreme Court found that observing the following nine things may help prevent an eyewitness from misidentifying an innocent person:
1. A police officer who conducts a live lineup or a photographic lineup with an eyewitness should not be familiar with the suspect because the officer may leak information by consciously or unconsciously communicating to the witness which person in the lineup is the suspect.
2. A police officer who conducts a lineup should begin with instructions to the eyewitness that the suspect may or may not be in the lineup and that the witness should not feel compelled to make an identification.
3. A suspect should be included in a lineup consisting of look-alikes because an array of look-alikes forces a witness to examine her memory.
4. The greater the number of choices in a lineup, the more likely it is that the procedure will function as a reliable test of the eyewitness' ability to distinguish the actual perpetrator of the crime from an innocent person.
5. Lineups should not contain more than one suspect; having multiple suspects increases the possibility of the eyewitness making a lucky guess.
6. Police officers should not signal to an eyewitness that she correctly identified a suspect; such confirmation can reduce a witness' doubt and engender a false sense of confidence. That sort of feedback can also falsely enhance an eyewitness' recollection of the quality of her view of a crime.
7. "Mugshot exposure" occurs when a witness initially views a set of photos and makes no identification but then later selects someone who appeared in a previous lineup. Studies have shown that while 15% of witnesses mistakenly identified an innocent person viewed in a lineup the first time, that percentage jumped to 37% if the eyewitness had seen the innocent person in a prior mugshot. Therefore, the police should avoid the practice of mugshot exposure.
8. "Mugshot commitment" occurs when a witness identifies a photograph that is then included in a later lineup. Studies have shown that once eyewitnesses identify an innocent person from a mugshot, a significant number then reaffirm their mistaken identification even if the real suspect is located in the lineup. Therefore, the police should also avoid the practice of mugshot commitment.
9. A "showup" is essentially a one-person lineup: a single suspect is shown to an eyewitness in order to see if the witness can identify the suspect. Showups often occur soon after a crime is committed. Many experts believe that compared to lineups showups fail to provide an adequate safeguard against witnesses with poor memories or those who are inclined to guess. That is because every time a mistaken identification occurs in a showup, an innocent person is, by definition, misidentified. Essentially, showups make it easier for eyewitnesses to mistakenly identify innocent people. Evidence that has been gathered casts doubt upon the reliability of showups that are conducted more than two hours after a crime has been committed. Thus, as with lineups, police officers who conduct showups should instruct witnesses that the person they are about to look at may or may not be the actual perpetrator of the crime and that they should not feel pressured to make an identification. That being said, lineups are still the preferred method of identification because of the inherent suggestiveness of showups.