08/31/2011 12:53 pm ET | Updated Oct 31, 2011

Why Eyewitness Memory Isn't All It's Cracked Up to Be (Part II)

In Part I of this series, I began recounting my experiences as an expert witness in a recent armed robbery trial. The two victims in the case, both White men, had described their assailant as a 20-something-year-old, clean-shaven Black man, 6'5" tall, with missing or broken teeth. The defendant standing trial, however, was 18 years-old, 5'10", goateed, and not the dentally challenged in the slightest.

My testimony focused on the scientific literature on eyewitness accuracy, the overarching conclusion of which is that memory is not a videotape. Whether we're observing a crime or a mundane conversation at the grocery store, we don't capture a snapshot of the events in question that we can then subsequently conjure up on demand. Rather, we remember the gist of what we observe, filling in the gaps with expectation, assumption, and information we learn later on.

This constructed nature of memory doesn't stop us from being confident in our own ability to remember events perfectly. I mean, I think I can recall things about the apartment I lived in as a toddler. I can even picture the railing around the balcony outside. But do I really remember any of this, or have I pieced together what feels like a recollection from old photographs, home movies, and stories my parents have told over the years?

I also have more recent memories that feel quite vivid, but for various reasons fail to stand up to close scrutiny. Like social interactions that I'd swear I can remember word-for-word, action-for-action, exactly as they occurred... except that my mental image of these events depicts them as if shown from a security camera. In my memory, I can actually see myself in the conversation from a detached perspective, which clearly isn't how I experienced the event.

The legal complications of the constructive nature of memory are clear: being an accurate eyewitness is far more difficult that we give it credit for. Consider the work done by the Innocence Project, a national organization dedicated to assisting wrongfully convicted individuals through DNA analysis. Thanks to their efforts, over the past two decades, more than 250 people have been exonerated by DNA tests that either weren't available at the time of their original trial (or just weren't conducted for some reason).

Of those 250+ cases, ¾ involved eyewitness testimony. That is, in close to 200 of these cases, at least one eyewitness (and sometimes more) pointed at an innocent person and said-quite confidently but erroneously -- "that's the guy." And these are just the cases that we know about.

Now, don't think that all these instances of mistaken identification are simply a matter of a witness only getting a fleeting glance of a masked culprit. Consider Jennifer Thompson, who, in the early 1980's was raped by a stranger in her own home. Her assailant spent an extended period of time in her apartment -- even carrying on several conversations with her. In fact, Thompson spent much of her attack strategizing about how best to remember what her rapist looked like, promising herself that she'd be able to identify him later.

She did identify someone in a police lineup, and very confidently at that. But she was wrong. As detailed in the book that she later co-wrote about the incident, the man she falsely identified would spend 11 years in prison before being exonerated by DNA analysis. Her co-author for her book? Ronald Cotton -- the very man she mistakenly identified years earlier, who now works alongside Thompson in her campaign to raise awareness of mistaken conviction.

Back to present day ... in the case in which I testified, many of the issues with the eyewitness identification didn't require an expert to explain. Like the disparities between how the victims described their attacker and the actual appearance of the defendant. And the fact that the victims had spent most of their 911 call describing in detail the sports car their assailant used to speed away from the scene, while the defendant had no car and lived just a few short blocks down the street.

But other issues weren't just common sense. Surveys of jurors suggest that many laypeople are unaware of the often tenuous link between an eyewitness's confidence and his or her accuracy. As I discussed in my testimony, research studies and actual case history -- like Jennifer Thompson's example above -- demonstrate that even the most confident of witnesses make mistakes.

Moreover, eyewitness confidence is malleable. That is, it changes over time, becoming inflated as the witness learns that the person he identified is someone whom the police like as a suspect. Or after talking with other witnesses. Or after reading media accounts of the crime or encountering the defendant in court during pre-trial hearings. Research has demonstrated that even the verbal response of the police officer who administers a photo array or lineup can make witnesses feel more confident in their identification.

Indeed, in my case the same witnesses who once tentatively identified the defendant in a photo array at 50-60% confidence were now testifying in open court that they were 80-90% sure that this was the guy.

But in preparing to testify, perhaps the most troubling aspect of the case to me was the photo array itself -- that sheet with 9 photos that had been presented to the victims for the purpose of eyewitness identification. When I looked at the photo array, something about it seemed fishy.

I couldn't quite put my finger on why, but for some reason the image of the defendant seemed to leap off the page. Perhaps because his face filled more of the frame than the photos of the other men? Perhaps because his head was cocked at an unusual angle? I wasn't entirely sure what it was, but I did know that something about the photo array just didn't look like a fair and balanced test of eyewitness memory. So the week before I testified, I put this photo array to the test...


Like this post? Then check out the website for "Situations Matter: Understanding How Context Transforms Your World" (available now for pre-order). You can also follow Sam on Facebook here and on Twitter here. Book trailer video below:

Subscribe to Breaking Alerts.
Don’t miss out — be the first to know all the latest news.