Ohio Court Admits Lie Detector Tests As Evidence

An anonymous reader writes "Last month, an Ohio court set a new precedent by allowing polygraph test results to be entered as evidence in a criminal trial. Do lie detectors really belong in the court room? AntiPolygraph.org critiques the polygraph evidence from the this precedential case (Ohio v. Sharma)."

Comments

Lie detectors are very unreliable

[slashqwerty]

The most common lie detector, the control question test, takes a set of baseline readings where the suspect is expected to tell the truth on some questions and lie on others. It then compares those results to the questions the examiner is most interested in. These tests have been shown to product accurate results about 65% of the time (that's per person tested).

Professional polygraphers will claim their test works 96% of the time. Those claims are bald-faced lies. Regardless of that we can take a look at what happens if the test really did work 96% of the time.

Some employers have been known to hire polygraphers to identify which employee may have been involved in some inside theft (or similar situation). The employer asks the polygrapher to test 50 employees. The odds that the tests will be correct with all 50 employees is 0.96^50=13%. So there is an 87% chance the test will accuse an innocent person...and that assumes the test is correct 96% of the time. What invariably happens is the polygrapher 'discovers' the culprit after the first few tests, packs up his things, and goes home. He identifies the suspect so quickly because the test is only right 65% of the time. Whether the accuracy is 65% of 96% the test will still point to a suspect even if none of the employees did anything wrong.

Re:Accuracy as against usefulness

[Kandenshi]

There are policing agencies out there who already do similar things. Despite it's absense, they may explain that there's incontrevertible evidence that shows that the suspect is guitly, they just want a confession so that the trial goes faster and with less fuss/humiliation for others/etc...

Turns out that one can get a fairly large number of confessions that way, much like you apparently desire. The problem is, it's not all THAT uncommon for the confessions to be lies. Innocent people will lie and confess to horrible, horrible crimes. And a confession given to a jury is a really really good predictor of them finding the defendent guitly. Even if there's little to no other evidence. People tend to believe confessions, which is sort of confusing since they have to reconcile the idea that "this is a dangerous lunatic with no morals and a willingness to kill" against "this is an honest man, who will condemn himself to jail by giving a confession". Still, they manage it.

Feel free to read a bit more about the subject of false confessions here, on some webnotes for a college class here or even here(this last one is perhaps more likely to cherrypick it's evidence, but what it says appears to be true).

False confessions are a rather worrying thing to me, as once a person confesses, the police have a tendency to cease looking for other potential guilty parties. While it's possible some other person will eventually be found guilty and you get released, it's not really something that The System tries for. Makes 'em look bad if they accidentally put someone in jail and gave 'em a whole bunch of publicity as a convicted rapist.

Re:Weight vs admissibility

[All_One_Mind]

I failed a polygraph when I was telling the truth. I was looking at 14 years in prison, so the pressure was intense and I was nervous as fuck. The end result: The polygraph said I was lying about not shooting some guy I had never met in the face.

I can't even imagine what would've happened if that would've been considered "evidence" admissible in court. I'd probably be in prison right now.