Witness Lineups

In a witness lineup, a witness is asked to identify a suspect. This tests the witness's ability to recognize, which is easier to do than freely recalling something from memory.

A lineup group is put together consisting of at least six foils, and among these is one target person. The target person is the suspect. The other foils are called distractors and are people we know to be innocent of the crime in question.

Getting it right matters. An American study reviewed 40 cases where people had been wrongly convicted of crimes and later exonerated due to the development of new technology, so-called DNA analysis. In 36 of these cases, the innocent had been convicted after being incorrectly identified by witnesses. Five of these people were sitting on death row awaiting execution. It is therefore extremely important that witness lineups are conducted correctly.

Types of lineups

A lineup can be carried out live or via photographs. Many believe that live lineups are better than photographs, but research shows this is not the case, provided the identification only concerns recognizing faces.

Lineups can be carried out where all the foils appear at the same time and stand lined up next to each other. This is called a simultaneous lineup. Foils can also be presented one at a time, letting the witness decide whether each one is the person in question. This is called a sequential lineup. Research shows that both methods result in the same rate of correct identifications. However, it also shows that the rate of incorrect identifications is much higher for simultaneous lineups than for sequential ones. This is likely because the witness points out the person they consider most similar to the image they have of the offender.

In some cases there may also be several offenders and several suspects. In these cases, it is important not to include multiple suspects in the same lineup. This makes sense, since the risk of an incorrect identification due to chance increases if there are several suspects in the lineup group.

Choosing distractors

When selecting distractors, it is important to base the selection on the witness's description of the suspect. If the witness has, for example, described a tall man with broad shoulders and medium-length brown hair, that is the description used when selecting the distractors. One should not try to find people who are as similar to the suspect as possible.

There are exceptions, however. For example, the suspect may have dyed their hair blond and cut it in an attempt to change their appearance. In that case, one does not want all the distractors to have medium-length brown hair while only the suspect has short blond hair. In this case, the selection of distractors is based on the suspect's appearance instead. One can also choose to conduct a photo lineup if a photograph of the suspect and their earlier appearance is available.

Important considerations

One thing that is good to do, though it can of course be difficult due to practical circumstances, is for the people instructing the witness to not themselves know which of the foils is the suspect. This way, they cannot influence the witness in any direction.

Witnesses should also be clearly told that it is possible the offender is not among the foils at all. A meta-analysis covering 2,500 participants and witnesses showed that false identifications decreased by about 40% when witnesses received this type of instruction.