Scott Fraser: The problem with eyewitness testimony

220,539 views ・ 2012-09-10

TED


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Translator: Joseph Geni Reviewer: Morton Bast
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The murder happened a little over 21 years ago,
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January the 18th, 1991,
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in a small
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bedroom community
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of Lynwood, California, just a few miles
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southeast of Los Angeles.
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A father came out of his house
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to tell his teenage son and his five friends
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that it was time for them to stop horsing around
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on the front lawn and on the sidewalk,
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to get home, finish their schoolwork,
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and prepare themselves for bed.
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And as the father was administering these instructions,
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a car drove by, slowly,
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and just after it passed the father and the teenagers,
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a hand went out from the front passenger window,
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and -- "Bam, Bam!" -- killing the father.
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And the car sped off.
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The police,
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investigating officers, were amazingly efficient.
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They considered all the usual culprits,
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and in less than 24 hours, they had selected their suspect:
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Francisco Carrillo, a 17-year-old kid
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who lived about two or three blocks away
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from where the shooting occurred.
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They found photos of him. They prepared a photo array,
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and the day after the shooting,
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they showed it to one of the teenagers, and he said,
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"That's the picture.
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That's the shooter I saw that killed the father."
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That was all a preliminary hearing judge had
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to listen to, to bind Mr. Carrillo over to stand trial
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for a first-degree murder.
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In the investigation that followed before the actual trial,
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each of the other five teenagers was shown
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photographs, the same photo array.
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The picture that we best can determine was probably
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the one that they were shown in the photo array
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is in your bottom left hand corner of these mug shots.
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The reason we're not sure absolutely is because
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of the nature of evidence preservation
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in our judicial system,
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but that's another whole TEDx talk for later. (Laughter)
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So at the actual trial,
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all six of the teenagers testified,
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and indicated the identifications they had made
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in the photo array.
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He was convicted. He was sentenced to life imprisonment,
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and transported to Folsom Prison.
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So what's wrong?
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Straightforward, fair trial, full investigation.
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Oh yes, no gun was ever found.
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No vehicle was ever identified as being the one
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in which the shooter had extended his arm,
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and no person was ever charged with being the driver
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of the shooter's vehicle.
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And Mr. Carrillo's alibi?
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Which of those parents here in the room might not lie
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concerning the whereabouts of your son or daughter
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in an investigation of a killing?
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Sent to prison,
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adamantly insisting on his innocence,
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which he has consistently for 21 years.
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So what's the problem?
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The problems, actually, for this kind of case
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come manyfold from decades of scientific research
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involving human memory.
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First of all, we have all the statistical analyses
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from the Innocence Project work,
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where we know that we have, what,
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250, 280 documented cases now where people have
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been wrongfully convicted and subsequently exonerated,
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some from death row, on the basis of later DNA analysis,
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and you know that over three quarters of all of those cases
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of exoneration involved only eyewitness identification
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testimony during the trial that convicted them.
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We know that eyewitness identifications are fallible.
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The other comes from an interesting aspect
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of human memory that's related to various brain functions
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but I can sum up for the sake of brevity here
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in a simple line:
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The brain abhors a vacuum.
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Under the best of observation conditions,
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the absolute best,
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we only detect, encode and store in our brains
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bits and pieces of the entire experience in front of us,
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and they're stored in different parts of the brain.
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So now, when it's important for us to be able to recall
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what it was that we experienced,
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we have an incomplete, we have a partial store,
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and what happens?
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Below awareness, with no requirement for any kind of
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motivated processing, the brain fills in information
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that was not there,
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not originally stored,
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from inference, from speculation,
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from sources of information that came to you,
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as the observer, after the observation.
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But it happens without awareness such that
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you don't, aren't even cognizant of it occurring.
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It's called reconstructed memories.
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It happens to us in all the aspects of our life, all the time.
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It was those two considerations, among others --
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reconstructed memory, the fact about the eyewitness fallibility --
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that was part of the instigation
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for a group of appeal attorneys
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led by an amazing lawyer named Ellen Eggers
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to pool their experience and their talents together
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and petition a superior court
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for a retrial for Francisco Carrillo.
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They retained me, as a forensic neurophysiologist,
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because I had expertise
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in eyewitness memory identification,
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which obviously makes sense for this case, right?
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But also because I have expertise and testify about
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the nature of human night vision.
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Well, what's that got to do with this?
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Well, when you read through the case materials
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in this Carrillo case,
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one of the things that suddenly strikes you is that
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the investigating officers said the lighting was good
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at the crime scene, at the shooting.
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All the teenagers testified during the trial
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that they could see very well.
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But this occurred in mid-January,
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in the Northern Hemisphere, at 7 p.m. at night.
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So when I did the calculations
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for the lunar data and the solar data
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at that location on Earth at the time of the incident
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of the shooting, all right,
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it was well past the end of civil twilight
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and there was no moon up that night.
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So all the light in this area from the sun and the moon
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is what you see on the screen right here.
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The only lighting in that area had to come
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from artificial sources,
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and that's where I go out and I do the actual reconstruction
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of the scene with photometers, with various measures
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of illumination and various other measures of
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color perception, along with special cameras
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and high-speed film, right?
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Take all the measurements and record them, right?
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And then take photographs, and this is what the scene
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looked like at the time of the shooting
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from the position of the teenagers
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looking at the car going by and shooting.
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This is looking directly across the street
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from where they were standing.
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Remember, the investigating officers' report said
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the lighting was good.
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The teenagers said they could see very well.
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This is looking down to the east,
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where the shooting vehicle sped off,
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and this is the lighting directly behind the father
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and the teenagers.
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As you can see, it is at best poor.
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No one's going to call this well-lit, good lighting,
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and in fact, as nice as these pictures are,
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and the reason we take them is I knew I was going to have to testify in court,
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and a picture is worth more than a thousand words
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when you're trying to communicate numbers,
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abstract concepts like lux, the international measurement
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of illumination, the Ishihara color perception test values.
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When you present those to people who are not well-versed
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in those aspects of science and that, they become
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salamanders in the noonday sun. It's like
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talking about the tangent of the visual angle, all right?
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Their eyes just glaze over, all right?
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A good forensic expert also has to be a good educator,
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a good communicator, and that's part of the reason
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why we take the pictures, to show not only
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where the light sources are, and what we call the spill,
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the distribution, but also so that it's easier
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for the trier of fact to understand the circumstances.
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So these are some of the pictures that, in fact,
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I used when I testified,
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but more importantly were, to me as a scientist,
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are those readings, the photometer readings,
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which I can then convert into actual predictions
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of the visual capability of the human eye
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under those circumstances,
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and from my readings that I recorded at the scene
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under the same solar and lunar conditions
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at the same time, so on and so forth, right,
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I could predict
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that there would be no reliable color perception,
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which is crucial for face recognition,
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and that there would be only scotopic vision,
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which means there would be very little resolution,
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what we call boundary or edge detection,
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and that furthermore, because the eyes would have been
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totally dilated under this light, the depth of field,
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the distance at which you can focus and see details,
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would have been less than 18 inches away.
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I testified to that to the court,
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and while the judge was very attentive,
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it had been a very, very long hearing
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for this petition for a retrial, and as a result,
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I noticed out of the corner of my eye
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that I thought that maybe the judge was going to need
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a little more of a nudge
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than just more numbers.
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And here I became a bit audacious,
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and I turned
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and I asked the judge,
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I said, "Your Honor, I think you should go out
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and look at the scene yourself."
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Now I may have used a tone which was more like a dare
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than a request — (Laughter) —
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but nonetheless, it's to this man's credit and his courage
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that he said, "Yes, I will."
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A shocker in American jurisprudence.
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So in fact, we found the same identical conditions,
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we reconstructed the entire thing again,
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he came out with an entire brigade of sheriff's officers
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to protect him in this community, all right? (Laughter)
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We had him stand actually slightly in the street,
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so closer to the suspect vehicle, the shooter vehicle,
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than the actual teenagers were,
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so he stood a few feet from the curb
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toward the middle of the street.
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We had a car that came by,
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same identical car as described by the teenagers, right?
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It had a driver and a passenger,
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and after the car had passed the judge by,
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the passenger extended his hand,
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pointed it back to the judge as the car continued on,
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just as the teenagers had described it, right?
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Now, he didn't use a real gun in his hand,
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so he had a black object in his hand that was similar
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to the gun that was described.
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He pointed by, and this is what the judge saw.
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This is the car 30 feet away from the judge.
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There's an arm sticking out of the passenger side
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and pointed back at you.
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That's 30 feet away.
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Some of the teenagers said that in fact the car
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was 15 feet away when it shot.
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Okay. There's 15 feet.
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At this point, I became a little concerned.
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This judge is someone you'd never want to play poker with.
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He was totally stoic. I couldn't see a twitch of his eyebrow.
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I couldn't see the slightest bend of his head.
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I had no sense of how he was reacting to this,
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and after he looked at this reenactment,
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he turned to me and he says,
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"Is there anything else you want me to look at?"
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I said, "Your honor," and I don't know whether I was
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emboldened by the scientific measurements that I had
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in my pocket and my knowledge that they are accurate,
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or whether it was just sheer stupidity,
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which is what the defense lawyers thought — (Laughter) —
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when they heard me say,
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"Yes, Your Honor, I want you stand right there
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and I want the car to go around the block again
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and I want it to come and I want it to stop
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right in front of you, three to four feet away,
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and I want the passenger to extend his hand
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with a black object and point it right at you,
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and you can look at it as long as you want."
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And that's what he saw. (Laughter)
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You'll notice, which was also in my test report,
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all the dominant lighting is coming from the north side,
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which means that the shooter's face would
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have been photo-occluded. It would have been backlit.
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Furthermore, the roof of the car
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is causing what we call a shadow cloud inside the car
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which is making it darker.
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And this is three to four feet away.
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Why did I take the risk?
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I knew that the depth of field was 18 inches or less.
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Three to four feet, it might as well have been
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a football field away.
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This is what he saw.
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He went back, there was a few more days of evidence
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that was heard. At the end of it,
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he made the judgment that he was going to grant
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the petition for a retrial.
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And furthermore, he released Mr. Carrillo
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so that he could aid in the preparation of his own defense
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if the prosecution decided to retry him.
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Which they decided not to.
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He is now a freed man. (Applause)
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(Applause)
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This is him embracing his grandmother-in-law.
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He -- His girlfriend was pregnant when he went to trial,
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right? And she had a little baby boy.
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He and his son are both attending Cal State, Long Beach
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right now taking classes. (Applause)
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And what does this example --
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what's important to keep in mind for ourselves?
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First of all, there's a long history of antipathy
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between science and the law
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in American jurisprudence.
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I could regale you with horror stories of ignorance
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over decades of experience as a forensic expert
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of just trying to get science into the courtroom.
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The opposing council always fight it and oppose it.
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One suggestion is that all of us become much more
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attuned to the necessity, through policy,
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through procedures,
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to get more science in the courtroom,
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and I think one large step toward that
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is more requirements,
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with all due respect to the law schools,
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of science, technology, engineering, mathematics
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for anyone going into the law,
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because they become the judges.
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Think about how we select our judges in this country.
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It's very different than most other cultures. All right?
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The other one that I want to suggest,
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the caution that all of us have to have,
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I constantly have to remind myself,
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about just how accurate are the memories
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that we know are true, that we believe in?
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There is decades of research,
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examples and examples of cases like this,
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where individuals
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really, really believe. None of those teenagers
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who identified him
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thought that they were picking the wrong person.
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None of them thought they couldn't see the person's face.
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We all have to be very careful.
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All our memories are reconstructed memories.
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They are the product of what we originally experienced
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and everything that's happened afterwards.
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They're dynamic.
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They're malleable. They're volatile,
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and as a result, we all need to remember to be cautious,
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that the accuracy of our memories
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is not measured in how vivid they are
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nor how certain you are that they're correct.
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Thank you. (Applause)
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