Proper sleep can influence an eyewitness' ability to correctly identify a guilty person, suggests a recent study.
Researchers from Michigan State University in East Lansing, U.S. found that eyewitnesses to a crime who sleep before being given a lineup are much less likely to pick an innocent person out of a lineup - at least when the perpetrator is not in the lineup.
This study is the first scientific investigation into how sleep affects eyewitness memory of a crime, said lead author Michelle Stepan, a doctoral student in psychology.
"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 added.
The team conducted an experiment in which about 200 participants watched a video of a crime (a man planting a bomb on a rooftop) and then, 12 hours later, viewed one of two computer lineups of six similar-looking people.
One lineup included the perpetrator; the other lineup did not.
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Some participants watched the crime video in the morning and viewed a lineup that night, with no sleep in between. Others watched the crime video at night and viewed a lineup the next morning, after sleeping.
The results revealed that the participants who had slept identified an innocent person 42 percent of the time - compared to 66 percent for participants who had not slept.
"This is the most interesting finding of the study - that individuals are less likely to choose an innocent suspect after a period of sleep when the perpetrator is absent from the lineup," Fenn said.
Fenn noted that sleep may not help you get the right guy, but it may help you keep an innocent individual out of jail.
"These findings tell us that sleep likely impacts memory processes but that it might also impact how people search through a lineup, and those search strategies might be a critical factor when the perpetrator is not in the lineup," she said.
The results appear in journal of PLOS ONE.