August 16, 2003
Lie Detector Tests More Accurate Than Juror Judgement

Richard A. Muller says that while lie detector tests are not admissible in court due to their error rates...

It is also true that this accuracy figure implies that only 85 percent of truth-tellers will be exonerated; 15 percent will be falsely accused of lying. That is why the National Academy of Sciences’ report came down so hard on the process.

...we rely instead on the ability of jurors to measure the honesty of testimony and the jurors have even higher error rates.

To do this, they were told to take into account “the demeanor” of the witness, his directness in answering questions, and anything else that they thought indicated truthfulness. Ironically, scientific tests show that the average person’s probability of catching a lie in this way is only “slightly better than chance,” according to Ekman. Moreover, the jurors who use this approach have the conviction that their accuracy is near 100 percent, despite their knowledge that most witnesses are extensively coached in methods of appearing sympathetic and truthful—in other words, in methods to defeat the system.

The jury trial system is in great need of technologies that would make it more accurate. Juror tests could be developed that use Statistical Prediction Rules (SPRs) to choose jurors who are more capable of discerning the truth. Additional SPRs could be developed for analysing types of evidence and even of testimony. Our criminal justice system is based on the false conceit that we are excellent judges of character and of other forms of evidence.

Share |      Randall Parker, 2003 August 16 11:47 AM  Expert Systems

john said at August 16, 2003 4:25 PM:

so what is the lab juror failure rate?
what is the court juror failure rate as measured by killers exonerated later by DNA or other good afterconviction evidence?
this article jumps around too fast from topic to topic without good summary statistics and head to head comparisons. But , it raises great points. Just needs to answer those points more fully and clearly.

John Moore (Useful Fools) said at August 16, 2003 5:28 PM:

One thing that may improve justice is the increase in saved surveillance videos, as the country becomes more of a surveillance nation. From web-cams to anti-burglary cams to traffic cams, more and more crimes are being caught on tape - making the job of deciding guilt more accurate.

razib said at August 17, 2003 5:23 PM:

well, aren't 95% of crimes plead out? doesn't even get to the point of a jury....

David Weisman said at August 19, 2003 8:35 PM:

By that logic you could decide to accept jurors who were better at detecting lies and declining others. Clearly contrary to our whole jury system.

Randall Parker said at August 19, 2003 10:09 PM:

Why is in contrary to our jury system to reduce the chance that jurors will make mistakes?

Larry Saunders said at October 9, 2008 2:06 PM:

Neuroscience tells us that people have very excellent built-in lie detector capabilities. Moreover, the collective wisdom of a group of people on a jury far exceeds that of any single person. The fact is that over and over again, lie detector tests have been shown to be on a par with reading tea leaves. On the other hand, jurors are actually quite good at determining who is telling the truth and who is not.

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