Sitting in her office at Claremont Graduate University in California, cognitive psychologist Kathy Pezdek flips open a case file for an upcoming homicide trial-a drive-by shooting in which the victim's girlfriend will take the stand to identify the accused. The defense has retained Pezdek as an expert on the reliability of eyewitness memory.
"For starters," says Pezdek, "I see here that the first time the girlfriend talks to the police, she tells them, 'I didn't actually see the guy's face.' "
That's a problem for the prosecution, obviously. Within hours of the crime, however, police pull someone off the street, stick him in a squad car and show him to the witness. "It could be him," the girlfriend says.
Two days later, she views a photo lineup. "Of course," says Pezdek, "she picks out the only guy who would look familiar to her." It's the man she saw in the police cruiser. "And the police tell her, 'Yeah, you picked the right guy.' "
Pezdek has no doubt that, with coaching, the prosecution will have a confident eyewitness on the stand. "Problem is, the jury hasn't seen her progression from 'I never saw his face,' to 'it could be him' to 'yes, I'm sure.' "
In other words, the prosecution will present to the jury a fine courtroom drama, sans the editing job that produced the final cut.
Our memories are, to some degree, like a final-cut videotape: Research confirms that each of us continually edits and splices recollections, replacing one "picture" with another, sometimes with a little outside assistance. "Memory is a creative event, born anew every day," says Elizabeth Loftus, a University of California, Irvine, psychologist who is a leading expert on the malleability of eyewitness testimony. "You fill in the holes every time you reconstruct an event in your own mind."
A decade of intensive research has taught Loftus and her colleagues how easy it is to plant false memories. In experiments, they've demonstrated that few people, if any, can reliably distinguish between memories of something they've been shown and something they've been asked to imagine.
The trick works on the public at large too. Forensic psychologists weren't surprised that what seemed to be a mass hallucination followed the first D.C. sniper shootings last fall. Jumpy residents jammed the FBI's hotline with recollections of white vans and box trucks brimming with guns. All it took to set the editing rooms working were news reports of such a vehicle seen speeding away from an attack.
Not that prompting is even necessary. According to memory-reconstruction expert Charles Weaver at Baylor University, we tend to alter a few details of memory with every early replay. Moreover, the retouch job of a vivid imagination can come across as far more compelling than the washed-out "first take" of our physical senses.