The polygraph is used as a lie detector by police departments, the FBI, the CIA, federal and state governments, and numerous private agencies. The underlying theory of the polygraph is that when people lie they also get measurably nervous about lying. The heartbeat increases, blood pressure goes up, breathing rhythms change, perspiration increases, etc.There are three basic approaches to the modern test:
1. The Control Question Test- "This test is often used to determine whether certain criminal suspects should be prosecuted or classified as uninvolved in the crime" (Caroll0.
2. The Direct Lie Test- detects lying by comparing physiological responses when the subject is told to deliberately lie to responses when they tell the truth.
3. The Guilty Knowledge Test- This test compares physiological responses to multiple-choice type questions about the crime, one choice of which contains information only the crime investigators and the criminal would know about.
Work Cited: Carroll, Robert. Criminal Profiling: Cold Reading for Cold Cases. American Psychological Association, 2007.
I always love seeing articles about polygraph machines, they have always interested me because of their use. I'm pretty sure a lot of courts cannot use them for a basis for conviction but they do help the investigators a lot. I think somewhere I heard that in mid evil China they would ask the accused a series of question and then press a burning piece of metal to their tongue for two seconds. If they got burned that would mean they were guilty and if they didn't they were innocent. The idea is similar to that of the modern polygraph machines. The body naturally goes threw subconscious and uncontrollable changes when lying.
ReplyDeleteAlthough polygraph tests are a common usage in todays society i never knew there a guilty knowledge type test. You always hear lie detector tests being used on such shows as jerry springer and steve wilkos, but they never get in to details of the actual test. It is interesting to think about how these tests even came about.
ReplyDeleteThe Polygraph is a really good invention and has probably helped to put a lot of bad people in jail where they belong! I do wonder how they can surely know that the results are accurate and there isn’t just some error on the machine. Also, if there is any way to mess with the machine and confuse it and really have a person who is guilty come out innocent?
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