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Problems with Eyewitness Testimony

For quite a long time, extensive empirical work in psychology, sociology, and behavioral economics has been revealing that many of the law’s most cherished rules are faulty. They are based upon mistaken assumptions about human behavior. They are often flat out wrong. And yet they persist.

Ariely Predictably IrrationalThe work of Daniel Kahneman and Amos Tversky has shown that the human mind operates with all sorts of biases and heuristics that lead to systematic errors in judgment and perception.  As Dan Ariely put it in a recent work, Predictably Irrational (2008): “[W]e are not only irrational, but predictably irrational . . . our irrationality happens the same way, again and again.” (p. xx).  Richard Thaler and Cass Sunstein describe many of these systematic blunders in human judgment in their book, Nudge (2008).

As these studies increasingly make their way into legal scholarship, they are proving that many existing legal rules don’t work as they should.  And this is more than a mere normative critique.  The rules just fail because people don’t act or think the way the law thinks they ought to.  In fact, what we’re learning about the way people act and think is often counterintuitive.  It is hard to grasp and hard to deal with.

NudgeThis research should be undermining many legal rules at their very foundations.  Yet the legal rules don’t seem to be shaken despite their foundations being annihilated.

In many domains, when something is proven flat wrong, it is confronted and dealt with.  If evidence shows that bleeding the patient isn’t a good cure for disease, then we move on and stop doing it.  But in law, if the evidence shows that a rule doesn’t work, what’s the response?  Often, it is to just accept the evidence with a grin and continue on.  If science were like law, we’d be talking about how the earth is round yet continuing to behave as if it were flat.

I think that it is time to hold the law up to the light of contemporary understanding and bring it into the 21st century.  Many legal rules are based on crusty assumptions made back in the 19th century, such as the M’Naghten rule for insanity(1843).  Hardly any experts would contend that the  M’Naghten rule (inability to distinguish right from wrong) is consistent with contemporary understandings in psychology.  The law of evidence is replete with faulty psychological assumptions.  So many areas of law don’t stand up to modern understandings of science, statistics, psychology, or empirical studies.

The example I want to focus on primarily is eyewitness testimony.  Countless studies have shown that eyewitness testimony is very unreliable, yet the law routinely permits convictions based solely upon eyewitness testimony.  I dug out my copy of Wrightsman’s Psychology and the Legal System (my edition is older than the one I’m linking to).  Here are some interesting facts:

As many as 80% of the eyewitnesses in some studies choose someone, even when none of the lineup members is the true criminal. (p. 148)

Buckhout (1975) staged a simulated crime on a television news broadcast and asked members of the viewing audience to phone in their choise of suspects shown shortly after the crime.  Out of 2145 viewer-witnesses who called in, only 14.7% were correct, an accuracy rate that was no different from the one achieved by simply guessing. (p. 148)

Also, victims of crime are less reliable in identifying the perpetrators than bystanders (p. 149).  Compounding the problem:

Jurors put too much emphasis on witnesses’ statements about the confidence of their identifications.  In fact, Cutler, Penrod, and Stuve (1988) found that, for laypersons, the witness’s level of confidence was the most important criterion for judging the witness’s truthfulness. . . . [But] an eyewitness’s confidence is not a strong indication of accuracy. (pp. 149-50)

This is a big problem, yet the law doesn’t deal with it.  Instead, the law does just the opposite — it prevents defense attorneys from introducing evidence of all these studies that undercut the accuracy of eyewitness testimony, thus preventing jurors from being properly educated.

Perhaps the law could adopt one of the following rules:

1. Eyewitness testimony could be completely barred as more prejudicial than probative.

2. Eyewitness testimony could be allowed only if corroborated.

3. Eyewitness testimony could be allowed, but defendants would be permitted to school the jury about the studies showing its unreliability.

Moving down this path would be difficult.  Imagine the case with the parent who witnesses the murder of her child right before her eyes.  She is the lone witness and says she’s absolutely certain it was the defendant.  Should her testimony be not allowed?  To bar the parent from testifying about what she saw would be incredibly difficult to do — it seems almost inhumane.

But that’s what the studies are showing us.    Reforming the law so that it reflects contemporary understandings of psychology and human behavior is a difficult and daunting task.  But the law needs to be modernized.  It should be rationalized.

Originally Posted at Concurring Opinions

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This post was authored by Professor Daniel J. Solove, who through TeachPrivacy develops computer-based privacy training, data security training, HIPAA training, and many other forms of awareness training on privacy and security topics. Professor Solove also posts at his blog at LinkedIn. His blog has more than 1 million followers.

Professor Solove is the organizer, along with Paul Schwartz, of the Privacy + Security Forum and International Privacy + Security Forum, annual events designed for seasoned professionals.

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