A new study published in the PLOS ONE exposed the influence of sleep on eyewitness’s ability to pick a convict out of police lineup. It states that eyewitnesses to a crime who sleep before being given a lineup are much less likely to choose an innocent person out of a lineup.
“It's concerning that more people aren't making the correct decision during lineups; this suggests our memories are not super accurate and that's a problem when you're dealing with the consequences of the criminal justice system,” Stepan said. “Putting someone in jail is a big decision based on somebody's memory of a crime.”
The study, involved about 200 participants watched a video of a crime. Then, 12 hours later, they have given with one of two computer lineups of six similar-looking individuals, in which one lineup included the perpetrator.
Some participants were made to watch the crime video in the morning and view a lineup at night, without sleep in between, while the rest watched the crime video at night and given a lineup following day, after a night of sleep.
When the perpetrator was absent from the lineup, participants who had slept identified an innocent person 42% of the time — compared to 66% of participants who had not slept.
Kimberly Fenn, director of MSU's Sleep and Learning Lab said, the most exciting finding of the study that people are less likely to pick an innocent suspect after a period of sleep when the convict is not in the lineup. It is relevant because wrongful convictions too often stem from an improper eyewitness identification of a suspect who did not commit the crime.
When the perpetrator was in the lineup, there was no much difference in the ability of sleep and no-sleep groups to choose the perpetrator. Both groups correctly identified the offender about 50% of the time.
In perpetrator-absent lineups, use of relative strategy could increase the incorrect identification than the absolute strategy, Stepan noted. The findings reflect the influence of sleep on memory processes, it might also impact how the eyewitness search through a lineup and those search strategies might be a crucial factor when the convict is not in the lineup, she added.
The study results reflect changes in memory strength and decision-making strategies after sleep. The participants in the sleep group were more likely to use an absolute strategy, in which they analyze each person in the lineup to their memory of the suspect, while participants from no-sleep group, were more likely to use a relative strategy, in which they compare the people in the lineup to each other to identify who most resembles the convict relative to the others.
“Sleep may not help you get the right guy, but it may help you keep an innocent individual out of jail,” Fenn said.