Monday, June 11, 2007

Does The Polygraph Test Work?

It would be great if the polygraph test, otherwise known as the lie detector test, really worked.Certainly Melvin Foster would be happier. In 1982, when FBI profilers thought a taxi driver might be the Green River Killer, local police targeted Foster - a taxi driver - as a suspect. Foster generously agreed to a polygraph test, which he unfortunately failed.
It was unfortunate because he was entirely innocent.

Meanwhile, during a period of two to three years, the Green River Killer murdered four dozen or more women near Seattle and Tacoma, Washington. Gary Leon Ridgway was briefly a suspect, and he was given a polygraph test in 1984. It was determined that he was telling the truth about his innocence. Unfortunately, in this case, he was the killer, and he was free to keep killing, which he did.

In 2001 DNA evidence (and other evidence) finally proved that Ridgway was the killer. In 2003 he confessed, pleading guilty to 48 murders. After more than 20 years, Melvin Foster was finally cleared in the crimes.

Of course, the police never could gather enough evidence to arrest or prosecute Foster - this is usually difficult when the suspect is innocent. But Foster was under a cloud of suspicion for more than 20 years. In 2003, according to an article in the King County Journal, Foster asked the King County Sheriff's Office to finally "apologize and return his rock tumbler and all the rest of the stuff police took from his home in 1982."

It would be great if this didn't happen often, but how would we know? There are other stories about innocent people identified as suspects due to a failed polygraph test, but those are just the ones where the truth comes out. If Ridgway had not been caught, many people would still think Melvin Foster was the Green River Killer.

Perhaps many cases are left like that, with a cloud of suspicion over an innocent person. And what do people think if you fail a polygraph test? That you are guilty, or you must know something, since you are lying. And what do they think when you get the more common result of "inconclusive?" Many think, well, you didn't pass, so you must be guilty or know something. Isn't this what many of us really think when a criminal suspect or "person of interest" in the news can't pass the polygraph?

It would be of some value if the test at least consistently pointed out the real criminals along with few innocent people it wrongly identifies? But in addition to the example above, consider the numerous famous spies who passed the polygraph tests they were given (Ignatz Theodor Griebl, Karel Frantisek Koecher, and Jiri Pasovsky, among others). Many hardened criminals have also proven their ability to lie and still pass the polygraph.

"The US is, so far as I know, the only nation which places such extensive reliance on the polygraph....It has gotten us into a lot of trouble." - A quote from convicted spy (double-agent) Aldrich Ames, who passed two polygraph tests while spying for the Soviet Union.

By the way, most scientists don't believe in the effectiveness of the polygraph test. They consider it to be junk science. Of course it can "work" in some cases. Any lie detecting technique which points at enough possible liars will identify some of them, right? Even flipping a coin will produce an accurate result in some cases.

Is that good enough? What if you are telling the truth? Should you take the test just because you are innocent? Maybe not. If you rely on the polygraph test to prove your innocence, you're gambling with your reputation.

Labels: , ,


Anonymous Anonymous said...

Nice blog and nice post :).
Accountants in London

February 29, 2012 at 5:59 AM  

Post a Comment

<< Home