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Based on research by Malpass, R. S. & Devine, P. G. (1981) written by Mara Rowcliffe, MS.
Eyewitnesses’ identifying a perpetrator from a line-up is standard police procedure. Yet many prison inmates whose convictions hinged on eyewitness identification have later been proven innocent by DNA testing.
Doubting eyewitness accuracy in the lineup procedure, psychologists Roy Malpass, and Patricia Devine, staged a crime in the middle of a lecture. A man (who was actually hired by the researchers) entered the lecture hall, exchanged heated words with the instructor and knocked over a rack of machines before running off. Each audience member was then asked to identify the man in a lineup.
Results showed that the accuracy of the witnesses’ identifications depended on the instructions. Researchers gave two subtly different instructions: One implied that the witness had to choose among the suspects in the lineup, while the other implied that the witness did NOT have to make a choice. The real “criminal” was in the lineup only half the time.
The researchers found that telling witnesses they didn’t have to choose a suspect led to fewer false identifications — but importantly, that instruction did not hinder witnesses’ ability to make accurate identifications.
Innocent people have been executed due to eyewitness errors.
Malpass, R. S. & Devine, P. G. (1981). Eyewitness identification: Lineup instructions and the absence of the offender. Journal of Applied Psychology, 66, 482-489.
For more details see:
American Psychological Association, April 2014