DNA testing has played a huge role in how cases are tried and how defendants are convicted. Since this forensic analysis has been introduced into the trial process, it has shed light on a huge problem in our criminal justice system: the inaccuracy of eyewitness reports. Of the hundreds of cases in which convicts have been exonerated through DNA testing, more than 70 percent of these involved eyewitness misidentification.
Why memory is unreliable
According to a recent report, there are a number of factors that can influence our memory of an event. Situational conditions—such as dim lighting or a distant view of the incident—can reduce visual accuracy. Additionally, we may focus on certain details and overlook others. For instance, if someone enters a bar waving a gun, you might focus your attention on the gun rather than the perpetrator’s face. Or if, while in a crowded bar, you hear a gunshot and a person near you yell “he’s got a gun!”, then you might misremember having seen a robber holding a gun.
The reason for this inaccuracy lies in the way our brains work. We don’t absorb partial details of an event and store those incomplete fragments in our minds. Instead, our brains take the information that’s provided—the sight of a gun, the sound of people screaming—and fill in the rest of the picture for us, thereby creating a complete event that makes sense to us.
Impacts on eyewitness testimony
The report shows that the more you’re asked to recall a memory, the more likely it is to change or be lost. Witnesses are asked to recall a memory many times—during police line-ups, at meetings with attorneys—before ever testifying about that memory in court. Come time for the trial, the witness has had many occasions to recall the event—and thus many opportunities to construct a clear picture of what happened. This rehearsal tends to boost their confidence during testimony. And confident witnesses influence juries.
The problem, according to psychologist Dan Kahneman, is that highly confident testimonies only show that a witness has filled in a complete picture for themselves—not that the picture they’ve created is accurate.