How accurate are lie-detector tests?
There is another technique that appears to be more limited, but much more limited than tradition lie detector called Brain Fingerprinting.
http://en.wikipedia.org/wiki/Brain_fingerprinting
Brain Fingerprinting doesn’t try to distinguish between truthful answers and lies and doesn’t even involve asking questions. Brain Fingerprinting is based on the theory that the brain processes unknown information differently from familiar information and this difference can be detected by an EEG.
The limitation is that the police have to have information that hasn’t been publicly released and would only be familiar to the perpetrator of the crime. For instance; if a suspect claims to have witnessed a crime, there may be no way to distinguish him from the perpetrator. In some cases, the police may not have any information about the crime to use for a brain fingerprinting test.
Within those limits, the advocates of this technique claim accuracy of greater than 99% and the evidence has been admitted in court in some cases.
Back in the 1970s, I knew people who claimedf to have beaten the tests by keeping a nail in their shoe and pressing on it with their toes at critical questions and, oddly, by taping a bar of a certain brand of soap under an armpit. I forget the brand, but the lady who swore by this one said it had to be a certain brand and no other. These were all people taking polygraphs for employment screening and wanting to hide their recreational drug use. Myself, I’ve never taken a polygraph, so I don’t know what to make of these claims, but I’ve always found them dubious.
Well, they would say that, wouldn’t they? Were they using their own “brain fingerprinting” techniques when they said it? I don’t care what success rate they claim to have, I want to see it working.
But not in all; why would that be?
Siam Sam, the technique with the nail is to induce stress on your control questions and then release pressure on the actual questions so that your baseline shows the same level of stress as the “guilty” questions.
I am not familiar with the bar of soap method.
I would expect that an examiner who saw certain patterns in the results might be able to determine if some sort of evasion technique were being used, but not able to conclude lying on the pertinent questions because of it. However, if you received indicators of evasion, that would either be disqualifying right there, or warrant further questioning and more stringency.
Good question – have there been cases where “brain fingerprinting” has been available but has not been allowed as evidence?
I found this reference:
http://www.yjolt.org/files/roberts-9-YJOLT-234.pdf
It looks like there were two major cases. In the James Grinder case, he changed his plea to guilty when confronted with the brain fingerprinting evidence, so there was no ruling on the admissibility of Brain Fingerprinting. In the Harrington case, the Judge ruled the Brain Fingerprinting Evidence admissible to indicate that Harrington was innocent, but it wasn’t tested in court, because the court ordered a new trial, and the state decided it didn’t have enough evidence to retry the case.