Eyewitness testimony is considered one of the most valuable elements of a criminal investigation, but our memories are often wrong — 70% of convictions overturned with DNA evidence contradicted eyewitness testimony — because of how our brains process information, per Ars Technica.
How an eyewitness goes wrong: A study at the Salk Institute for Biological Studies found that our memories of traumatic events can often be based around our expectations of that event — for example, if a robbery occurs, a witness might say that they saw a gun simply because they expect one to be present. And memories can be slightly altered with each successive recall of an event as eyewitnesses try to create a picture that makes sense, rather than what they actually saw.
How to fix the process: The study pegs the initial suspect identification in a lineup as a primary point of focus, suggesting it should be administered by police with no connection to the case, videotaped for the future, and contain specifics on the witness' confidence level.