Billy is in jail for a crime he didn't commit. However, Steve, a credible member of the community, puts him at the scene of the crime, where he is accused of causing property damage. Steve identified Billy through a police line-up, and is positive on his decision. How is this possible? A little phenomenon called unconscious transference.
Unconscious transference occurs when a bystander, familiar with a criminal through another avenue, recognizes the suspect and places this familiar person at the crime, to the police, and in his or her own mind. This typically occurs when the bystander has had an encounter with the suspect that is not too vague or too specific. This could be as simple as seeing the person momentarily around town. Or it can also occur during police questioning, if the person sees a photo of the suspect then is introduced to them again in the physical line-up.
The latter occurs in great percentages in controlled studies where a person is shown a video of a crime, and then asked to pick out the perpetrator. Research indicates that if a bystander from the video is offered as one of the photos, that there is a high probability they will be chosen. However, in real life, it is much less likely that this will occur than in a controlled study. This is due to practices by most police agencies to use photos from inmates, and licenses from around the country.
The more promising possibility for unconscious transference, would then be familiarity based on previous interactions with the individual. Let's take a look at an illustration, using the possible scenario between Billy and Steve, for illustration.
Billy works at a little mom and pop shop downtown. He stocks the shelves primarily during the week. Two weeks prior to the incident involving property damage to a local bike shop, Steve stopped by to pick up some bread, on his way home. He is only in the store for a few moments. He has no recollection of the man who was filling the shelves with peanut butter, right next to him, as he decided whether to go with white or wheat.
Even though he did briefly speak to Billy, it was not a long enough encounter for either to remember. Their meeting was not important enough to recollect, yet Billy's face was put into Steve's unconscious.
When Steve witnessed the young man spray painting graffiti on the wall at the bike shop, it was dust. He didn't get a close sight of the perpetrator, although he did feel he might recognize him, if he saw him again. When Billy was brought in for the police line-up, due to his priors for vandalism, Steve recognized him immediately, from his brief encounter with him at the grocery store. However, since that meeting was completely inconsequential, Steve associated this familiarity with the crime. He fully believes that this is the person he saw spray painting the wall. Based on this testimony, Billy is imprisoned for a history that he can't seem to shake.
Diversity factors, such as age or race, also seem to play a part in higher rates of unconscious transference. When there is a difference in age or race, the error may occur in higher frequency. Thus if Billy was a younger adult, there is a greater chance that Steve would have mistakenly picked him as the perpetrator from the line-up.
An interesting factor, on the science end, is that people store information regarding facial recognition, and time and place in different areas of the brain. A quick online study offered by BBC Science, will give you an idea of your own retention of facial recognition. The test itself illustrates how people store information and what can be lost from certain areas of the brain with age or sleepiness.
All of these factors, linked with possible previous sight of the suspect, make unconscious transference a possibility of error in, what may seem ,a repeatable eye-witness testimony.