Sunday, December 20, 2009

Melvin Foster Versus The Polygraph

In my last entry, I discussed the unscientific and unreliable nature of polygraph tests. However, I never went over any specific examples of people whose lives were ruined because of a false positive or negative on a polygraph. So today, I present to you the sad tale of Melvin Foster.

The story begins back in the early 1980s in the state of Washington. A serial killer dubbed the Green River Killer murdered several young women in the Seattle / Tacoma area. He received his name due to the fact that he would leave the bodies around the Green River.

Anyway, a young Melvin Foster became interested in the case. He called the Green River Task Force in order to share information between the two parties and offer his help. Being that this is unusual behavior, the task force suspected Foster of being the killer since the killer would have an incentive to ask about his own case.

Foster was given a polygraph test and failed despite his innocence. The police used this to obtain warrants to search his house. He was convicted of the murders and spent close to two decades in jail. A DNA analysis performed in 2001 exonerated him.

They did eventually convict the real killer, Gary Ridgeway, shortly after. However, Foster lost nearly 20 years of his life due to a false positive on a polygraph test. I guess that was enough to convict him though.

Just say no to junk science!



  1. A properly conducted polygraph test is supported by science and by scientists. There are hundreds of scientific studies about polygraph accuracy published in prestigious journals. These experiments were conducted at universities and research facilities around the world.

    If a test is done poorly, in ways not supported by research, you can blame the examiner, but you shouldn't blame polygraph testing in general. If a surgeon botches an operation and the patient dies, you certainly wouldn't call all of medical practice a fraud.

    Most people are unaware of the vast amount of research which has been published. They are also unaware of the many cases in which innocent people, who had been arrested and indicted, were exonerated and set free as a result of passing polygraph tests.

    Louis Rovner, Ph.D.

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  3. There you go, DM. Someone who works in the polygraph industry assuring us they are accurate. Case closed....

    Now we can all get back to smoking cigarettes while installing asbestos!

  4. The National Academy of Sciences concluded that polygraph tests were unreliable and have a little better than a 50/50 chance of determining if someone is telling a lie. This was also the conclusion of the United States Congress Office of Technology Assessment.

    And even if it were 90% effective, its usefulness is still highly suspect. See my earlier post to understand why.


    Go read about it yourself:

    "We have reviewed the scientific evidence on the polygraph with the goal of assessing its validity for security uses, especially those involving the screening of substantial numbers of government employees. Overall, the evidence is scanty and scientifically weak." Page: 212

    "No direct scientific evidence assessing the utility of the polygraph. Indirect evidence supports the idea that a technique will exhibit utility effects if examinees and the public believe that there is a high likelihood of a deceptive person being detected and that the costs of being judged deceptive are substantial." Page 214

    (United States Congress Office of Technology Assessment):

    "Overall, the cumulative research evidence suggests that when used in criminal investigations, the polygraph test detects deception better than chance, but with error rates that could be considered significant."

  5. I went to the guy's wordpress site. He's clearly a shill for the industry.

    1. "He's clearly a shill for the industry"

      THAT statement. could also apply to people who try to 'debunk' this, case for the sick care industry.

  6. Luls, Dr. Rovner is a moron. I offer to take a test from him and I can pass it with flying colors or add as many false positives as he wants. It is not hard to beat a lie detector.

  7. 'Sup Monkey

    Happy Holidays, Seasons greetings and Happy New Year.

    I can't remember Dude's name right now, but that poor sap who was accused of the Olympic bombings in Atlanta's life was ruined by over zealous popo, I'm not sure what they said about his "test" if anything, but they combed over his whole life and made him out to be a loser. Truth is if they wanted to, it wouldn't be that hard to do the same thing to me? I don't trust any of that stuff?

    Later, feeno

  8. "He was convicted of the murders and spent close to two decades in jail. A DNA analysis performed in 2001 exonerated him."

    Source, please ?

    This is news to me and any other true crime reader.