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Should I Take a Polygraph (Lie Detector) Test?

If you are under investigation for a sex crime in Texas, you might be asked to take a polygraph test(a.k.a. “lie detector test”). The request might come from a police detective, the Texas Department of Family and Protective Services (DFPS) or Child Protective Services (CPS). While it is natural to want to clear your name quickly in a sex crime investigation, there are at least three (3) reasons why you should never take a government-sponsored polygraph examination, unless a criminal defense lawyer advises you to do so. The first reason is that an innocent person can fail a polygraph test. According to a report from the National Academy of Sciences, “[a] variety of mental and physical factors, such as anxiety about being tested, can affect polygraph results – making the technique susceptible to error.” Unfortunately, once you have failed a government polygraph test, there may be little you can do to convince the police, DFPS, CPS or a state or federal prosecutor that you are innocent.

A second reason why you shouldn’t take a polygraph test, unless your lawyer advises to do so, is that polygraph results are generally inadmissible in court. See, e.g., Tennard v. State, 802 S.W.2d 678, 683 (Tex. Crim. App. 1990) (Existence and result of polygraph test inadmissible). In other words: If you fail the test, government decision-makers will probably believe that you are guilty; but even if you pass, it is unlikely that a jury would ever get to hear the results. In that sense it can be a lose-lose proposition for a person whom the government requests to take a polygraph test.

A third reason not to take a polygraph test is that the investigators will probably ask you to sign a waiver of your right under the Fifth Amendment not to incriminate yourself. They may say, “All we have is the victim’s side of the story. Don’t you want to tell your side to clear your name?” Often law enforcement has no real interest in the truth – they want to use the lie detector to get a suspect talking. The interpretation of the test is totally subjective. The polygrapher may say he detected deception and ask if you’d like to explain yourself. The idea is to get you talking, and if it’s being recorded, that’s all the better for the people trying to send you to prison. Innocent statements can be twisted.

Another reason for declining a government polygraph test is that you can always take a private polygraph test arranged through your lawyer. My firm routinely arranges for private polygraph exams for clients who have been requested to take government-sponsored polygraph exams. The results of a private polygraph test may be kept confidential in the lawyer’s file. The results could also give the lawyer some idea about how the client might perform on a government test, under the right conditions. We often hire private polygraph examiners who have previously worked for police agencies. That allows us to confidently share good results with government decision-makers, as well as prepare the client for a government-sponsored polygraph test, if the client elects to take one. However, if a client fails a private polygraph test for any reason — for example, if the client gets nervous or suffers from test anxiety — our firm is under no obligation to share the results with anyone.