Why is a witness’s account so often unreliable? Partly because the brain does not have a knack for retaining many specifics and is highly susceptible to suggestion. “Memory is weak in eyewitness situations because it’s overloaded,” said Barbara Tversky, a psychology professor at Columbia University’s Teachers College in New York. “An event happens so fast, and when the police question you, you probably weren’t concentrating on the details they’re asking about.”

Hundreds of studies have cataloged a long list of circumstances that can affect how memories are recorded and replayed, including the emotion at the time of the event, the social pressures that taint its reconstruction, even flourishes unknowingly added after the fact.

While most of us tend to think memory works like a video recorder, it is actually more like a grainy slide show. Lost details, including imaginary ones, often are added later. One of the earliest and more famous experiments to demonstrate that memories are malleable was conducted by Elizabeth Loftus, a psychology professor at the University of California, Irvine, and an early pioneer of witness memory research.

In a 1974 study published in The Journal of Verbal Learning and Verbal Behavior, she asked participants to view films of fender-benders in which no car windows or headlights were broken. Later, the subjects who were asked how fast the cars were going when they “smashed” into each other — as opposed to “hit” — were more likely to report speeding and describe shattered glass they never actually saw.