Anonymous
Anonymous asked in Politics & GovernmentLaw Enforcement & Police · 1 decade ago

Why don't police allow suspects the right to take lie detector test and prove their innocence?

They think if more or less proves guilt, so allow suspects to prove their innocence with the same machine. If it works on the "guilty" it must work on the "innocent." Right?

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  • Anonymous
    1 decade ago
    Favorite Answer

    It's expensive to use a polygraph operator. If there is doubt to a suspects guilt or innocence, they will use a polygraph, if funding allows.

    In my 30 years, I've never know of a suspect being denied a polygraph in a major case IF there was some question as to guilt/innocence.

    Lots of times, suspects in very minor cases want to take a polygraph, not because they're innocent, but because they THINK they can beat the test. It's too expensive to offer that option in minor cases.

    Source(s): The Enforcer - I work with the Best of the Best to find the Worst of the Worst.
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  • Anonymous
    1 decade ago

    It does not work on the guilty or the innocent with any predictable results. You might as well call heads or tails on a coin toss.

    Recently the CIA, who gives all employees lie detector tests yearly, had a big problem with a bunch of double agents. The lie detector did not find them.

    I used to get lie detector tests on a lot of suspects but we did not use it for a finding of guilt or innocence. We used it as an investigative tool and because it impressed naive killers into confessing if they thought they flunked the box.

    Source(s): retired cop, 11 years homicide/sex detective
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  • Anonymous
    1 decade ago

    A polygraph measures stress so if someone is an accomplished liar they usually pass the test. On the other hand if suspect is nervous and stressed out by the interrogation process they can fail the test even if they're innocent. That's why lie detector test are inadmissible in court.

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  • 1 decade ago

    You have it wrong. It is usually the person's lawyer that will not let them take a lie detector test. Although it is inaccurate and thus, not admissible it court, it could point the officers in the right direction and help them get a conviction. That is why a defense lawyer will always tell their client to refuse a polygraph test.

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  • Anonymous
    1 decade ago

    Its not exactly an easy process, you need people who know how to operate it. Its not like a pregnancy test. Its also very time consuming. You are right, people should be able to take this test, but sometimes when something happens you might not be sure, and since the machine only reads brain waves, it cant see the past. They also suspect people could somehow trick this machine. The Jury system and physical proof is better most of the time.

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  • Ebby
    Lv 4
    1 decade ago

    A lie detector test is an investigative tool, it's not concrete evidence and not always accurate. Therefore the reason it is not admissible in court.

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  • 1 decade ago

    Polygraph tests are extremely innacurate. They only tell extreme signals of stress. That could mean anything, lying, their girlfriend was breaking up with them, they have a tumor.

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  • 1 decade ago

    Because polygraph tests are not admissible as actual evidence.

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  • 1 decade ago

    Polygraphs are notoriously inaccurate.

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