Many wrongful convictions are due to mistakes made during police lineups. In these lineups, investigators present a witness with either a group of possible suspects or a series of photos and ask them to identify the perpetrator. These results are often used as evidence in court and sometimes help put guilty people in jail. Unfortunately, tests like this rely on the accuracy of a witness’s memory and memory is not always as reliable as we think. Additionally, police lineups are conducted in a way that may bias witnesses to choose the person investigators suspect. Recent research has set forth two new guidelines to overcome these biases: the double-blind study and one-by-one inspection. Without following these procedures results of police lineups should be suspect.
When researchers conduct an experiment such as a taste test, they do what’s called a blind experiment. Subjects are given samples of food without being told what they are and then researchers ask them what they liked or disliked about the food. This is done so the results of the experiment aren’t biased by any prejudgment by the subjects. To achieve even more accurate results in drug trials, psychologists and other scientists often do “double-blind” studies. In these experiments, subjects are given either the drug being studied, or a placebo, and neither the subjects nor the researchers know which pills are real and which ones are fake. Scientists do this because any knowledge of the true medication could cause the researcher to accidentally clue the subject on which pill is genuine.
New research reveals the same process should be applied to police lineups. It’s conceivable – even likely – that a detective may accidentally indicate which person in a lineup is the person they suspect. If the witness picks up on this indication at all, the result of the lineup could be biased. This is obviously not the best way to reach an unbiased conclusion and seek a criminal conviction that could change an innocent person’s life forever.
The same studies also show when investigators present potential suspects to a witness, they should do so one-by-one rather than putting them all in a room together. This is because a witness must compare his or her memory to the appearance of the suspect rather than comparing all of the suspects to each other. Experiments done in 2011 showed that one-by-one inspection was the most likely to yield correct results and avoid police bias. See the Texas Law Enforcement Management Institute “Eyewitness Identification Model Policy.”
Thanks to DNA evidence we often learn people were wrongly convicted after a witness mistakenly picked them out of a police line-up. These tragic mistakes, which send innocent people to jail, result from the unreliability of human memory – a problem with no end in sight. Fortunately, police can limit the effects that human error have on these results by implementing these two simple procedural changes. Line-ups should be conducted like scienctific experiments; they should be double-blinded and suspects should be presented one-by-one.
Steve Gustitis has practiced criminal law exclusively since 1990. First as an assistant district attorney with Brazos County and then in private defense practice. He is Texas Board Certified in criminal law and committed to the aggressive and ethical defense of citizens accused of crime.
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