Flimsy eyewitness testimony

April 8, 2009 | By | 10 Replies More

Image by Erich Vieth

You often hear people claiming that the case is strong because there was an “eyewitness.”   It’s becoming increasingly clear, however, that eyewitness testimony is often worse than useless.   Modern DNA testing has exposed just how weak eyewitness testimony can be, as presented Radley Balko, in Reason:

Law and Human Behavior, false eyewitness testimony contributed to 77 percent of the 230 wrongful convictions exposed by DNA evidence over the last decade (the number of exonerations has grown since the study was conducted). These of course are only those cases for which DNA testing was available, which are usually murder and rape cases—crimes for which, generally speaking, there is also usually other evidence available. In crimes where investigators are more likely to rely only on eyewitnesses, robberies or muggings, for example, it’s likely that the problem is even more pronounced.


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Category: Law, law and order, snake oil

About the Author ()

Erich Vieth is an attorney focusing on consumer law litigation and appellate practice. He is also a working musician and a writer, having founded Dangerous Intersection in 2006. Erich lives in the Shaw Neighborhood of St. Louis, Missouri, where he lives half-time with his two extraordinary daughters.

Comments (10)

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  1. Danny says:

    As you can probably tell Erich, DI has made many posts that have drawn my interest as reflected in all my comments! Let me reiterate… I enjoy this blog a great deal!

    This post caught my attention. On the surface it's a fairly innocuous topic and made me wonder why you posted it. I have a hunch as to the significance… perhaps as it relates to eyewitness testimony of certain historical documents? Am I right? Care to elaborate?

    I'm guessing that you're not an empiricist and believe Hume was full of it?

    • Erich Vieth says:

      Danny: This post touches on one on one of my favorite topics: ways of knowing (and ways of not knowing). I happen to be a lawyer and I find it striking that perhaps the highest touted and most dramatic "way of knowing" expressed in courtrooms is so often wrong.

      Related post on the invalidity of many "confessions." http://dangerousintersection.org/2009/02/06/why-w

    • Erich Vieth says:

      "I’m guessing that you’re not an empiricist and believe Hume was full of it?"

      Heavens, no! David Hume is one of my heroes. Not that I agree with Hume on everything, but he dared to ask and explore the difficult simple questions of life.

      There's enough evidence out there for everyone to conclude (I believe) that we're not blank slates (see Steven Pinker on this, for example), and therefore strong empiricism isn't tenable. This is one of the issues with which Immanuel Kant struggled (Kant was inspired by Hume). The world we know results from a dynamic complex interaction between the stuff out of which we are made and the world "out there." I'm also convinced that Andy Clark is correct with his concept of the extended mind–minds are not bound by skin and skull; we "know" some things, I believe, even beyond those memories in our biological RAM.

      Although I still consider myself a student and a dabbler in many regards (this blog is my way of working things out), I have come to some conclusions. For the record, I don't believe that it's tenable to assert any form of knowledge based on anything "supernatural." Hope that helps. I know it's not crisp or tidy, but I invite you to check through some of the categories at this website and read some of the previous post on topics that might be relevant (such as psychology/cognition).

    • TonyC says:

      Erich: we “know” some things, I believe, even beyond those memories in our biological RAM.


      I'd be interested in hearing your views on that. My personal take is that we have a lot of 'hardwired' and instinctual knowledge – but it is subsumed by the acquired 'social' knowledge of our adult minds. In terms of knowledge, I'd be interested how exactly this 'other knowledge' to which you refer would be expressed or accessed.

      If knowledge is not accessible then it isn't really knowledge, is it? We can access some 'instinctual' knowledge (tracking a trajectory, for example). I'm not sure that the kind of knowledge to which you refer, however, is at all congruent with my description.

    • Erich Vieth says:

      Tony: Here are a few things to get you started: Follow this link to the post about Andy Clark's extended mind discussion here at DI. To dig in even further, consider Andy Clark's recent response to Jerry Fodor regarding Andy's latest book, Supersizing the Mind. I had the good fortune to attend several seminars taught by Andy Clark. A good place to start with the extended mind proposal is an earlier book by Andy, Being There. Carl Zimmer recently had complimentary things to say about the extended mind theory recently, at Discover Magazine.

    • TonyC says:

      Ah yes! I recall discussions about this (I think someone called it 'extrinsic intelligence').

      I think that such constructs (as described by Clark) are memetic in nature, and serve to 'extend' our cognitive abilities (similar to the use of Enki in 'Snowcrash' – a great novel by Neal Stephenson).

      However, that 'shared repository' is itself 'dumb'. We leverage that environment as we would a dynamic program – we load it, use it, and dump it – and maintain only enough of a kernel to be able to recognize when we might want to use it again! The intelligence is within ourselves. The external 'stuff' is simply storage. Some of it may be structured storage (social organization) but it is still just storage.

      In my opinion(!) if the ability or intelligence truly was external, then it would be available to anyone without the need to *learn*.

      What we need to learn is the 'kernel' that allows the use of the new program (using a calculator, for example).

      I don't think any of this invalidates my perspective on the 'mental gestalt' from which our identity emerges. In some ways it may even enhance it – we do, after all, learn to do many of these tasks 'autonomously' (ask anyone who learned to touch-type, or play an instrument, or perform a kata). These learned behaviors must 'execute' on a part of our mind that is directed (volitional) but the detailed actions are non volitional. In fact – if you try to think of the detailed behaviors, you get messed up!

      I've tried to teach finger-picking, and teaching the technique is non intuitive… some patterns are deeply embedded. I can play them – but only if I don't think about them!

      What does this all mean?

      I have absolutely no idea, but I'm excited to be around at a time when there is a likelihood of finding out!

  2. Danny says:

    Erich, that clears it up for me. I think I will read some of the back articles on this, because it interests me as well. Also, this topic makes more sense remembering that you're lawyer!

  3. Niklaus Pfirsig says:

    Years ago, I took some psychology classes in college. At the beginning of one class sessions, the students were subjected to a demonstration of the accuracy of eyewitness testimony.

    At the start of the class session, a young man, presumably a student from another class entered the room and and started arguing with the professor. The argument grew louder until the student pulled something from his coat poket and apparently stabbed to professor. The professor grabbed his side where he had been stabbed and fell to the floor as the student hightailed it out of the classroom.

    Within seconds the professor stood up, and announced "You are all witnesses to a crime, I need your statements". He gave everyone a questionaire to fill in, asking for descriptions of the perpetrator, the events and the weapon.

    Not one of the students gave a completely accurate description, and the descriptions varied considerably.

    Among other things, the descriptions of the weapon varied greatly. Most described some sort of knife, one or two thought is was a sharpened pencil. In reality, the weapon was a banana.

    • Erika Price says:

      Yeesh. I don't think a professor could get away with a charade like that anymore. No way does that satisfy ethical guidelines.

  4. TonyC says:

    I actually have personal experience of the failure of eyewitness testimony.

    When I was about 16, I was a victim of a gang mugging, very close to my home. There were many other witnesses, and two of the ten or so perpetrators were caught by an off-duty cop (who chased them down!) The primary case was against the one person who stabbed me with a knife.

    He was right in front of me for almost 3 minutes. (I was backed up against a wall, with the ten or so surrounding me).

    Despite the proximity and time – I got his height wrong, and his hair color & style wrong. I did get one thing right (he had a scar on the back of his hand) but that was luck more than anything else. I picked the wrong guy out of a line up (the guy I picked was actually on duty in the emergency room where I got myself repaired after the event!)

    If it weren't for forensic evidence left behind (he dropped his knife when I kicked him, which also cut him so the blade had a mix of our blood on it) he would never have been found (shopped by the two guys collared by the cop) or convicted.

    Sometime after that – I took a bunch of classes in improving memory. Didn't work very well – (I can't remember much from those classes, now!)

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