There's nothing more convincing than a positive, confident eyewitness in determining the outcome of a trial, said Elizabeth Loftus, a University of Washington professor of psychology and law who is a well-known expert on human memory.
Unfortunately, she said, an eyewitness can be both extremely persuasive and completely unreliable.
Loftus, the author of the books "Eyewitness Testimony" and "The Myth of Repressed Memory: False Memories and Allegations of Sexual Abuse," has testified as an expert witness at more than 200 trials, and has appeared on "Oprah," "60 Minutes," and many other talk and news shows.
Some of her work has been so controversial that, according to a 1996 profile in Psychology Today, "She has been called a whore by a prosecutor in a courthouse hallway, assaulted by a passenger on an airplane shouting, 'You're that woman!' and has occasionally required surveillance by plainclothes security guards at lectures."
There were no such fireworks at the College of William and Mary Law School, where Loftus spoke to a packed room Friday morning. Her audience was polite, interested, even friendly.
What she had to say was perhaps a little scary, though, in its implications about how profoundly untrustworthy our memories can be.
Loftus started with an example from the trial of Klaus von Bulow, accused of trying to kill his heiress wife. One bit of critical testimony at his first trial came from "Maria the maid," Loftus said. She said Maria recalled finding a black bag in a closet, looking inside and seeing a bottle of insulin.
But Alan Dershowitz, the famed Harvard Law professor who has represented many high-profile defendants, handled von Bulow's appeal. Dershowitz discovered that Maria's initial statement when questioned after Sunny von Bulow went into a coma was that she didn't know the bottle's contents because the label had been scraped off, Loftus said.
How does that happen, Loftus asked, that months later someone is positive she remembered something she earlier said she hadn't seen? "Human memory is malleable. It does not just work like a video camera," Loftus said.
Not only do people incorrectly remember the details of events they've witnessed, but it's pretty easy to make them believe they've seen things they haven't, Loftus said her research has shown.
Although a question may sound like it was designed to elicit information, it can also subtly deliver information to a witness, she said.
She cited, for example, research showing people's estimate of a car's speed depended on whether they were asked how fast it was going when it "contacted" or "smashed" the other car.
When the verb "contacted" was used, the average estimate was 32 mph, she said. It rose to 34 mph when "hit" was substituted, 38 mph when the verb was "bumped," 39 mph when the word was "collided" and almost 41 mph for the word "smashed."
What happens, Loftus explained, is that people remember the impact, but when a word like "smashed" is used, it enhances the image of the force involved, which the hearer can easily and unconsciously integrate into his memory. When the experiment was carried further, people were more likely to falsely remember there was broken glass at the scene if they had previously been asked how fast the car was going when it "smashed" into the other vehicle. It is very easy to alter or contaminate a witness' memory, Loftus concluded. Sometimes after a talk, people will tell her that the information she shares is dangerous, Loftus said. She asked if anyone in the room felt that way. Almost no one raised a hand.
Loftus said there were ethical guidelines involved in actively using that kind of knowledge to deliberately manipulate witnesses, but the law students would be wise to keep the information in mind for use defensively in evaluating eyewitness statements.
She said it would apply equally in both criminal and civil cases.