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Are Lie Detector Results Admissible in Arizona Courts?

Lie Detector

May 12, 2023

There are numerous legal and cop-themed shows on television, and many of their plots revolve around information from lie detector tests. However, this isn’t always the case in real life. While polygraph machines do exist and can be used in criminal trials, the results may not be admissible in Arizona courts. Read on to find out whether a lie detector test could impact your criminal case. 

What are lie detector tests? 

Lie detector tests, also known as polygraph tests, operate under the assumption that the machine can tell whether or not a person is lying. The machines track stats like heart rate, blood pressure, and breathing rate, as well as how much the test subject is sweating. Theoretically, these factors can tell the observer if the person is telling the truth or fabricating their answers. 

Are the results of a lie detector test admissible in Arizona courts?

In general, lie detector test results are not admissible in Arizona courts. That’s because they are not reliable enough to be considered scientifically sound. According to Daubert-Frye (Daubert v. Merrell Dow Pharmaceuticals, Inc. (9th Cir., 1995) 43 F.3d 1311 and Frye v. United States (D.C. Cir., 1923) 293 F. 1013, lie detector test results are only accurate 60 – 90 percent of the time. Polygraph machines also have a large margin for error. Some people can tell lies without setting it off while others can speak the truth and fail to pass the test.  

Are there exceptions to this rule?

Lie detector test results may be admissible in court only if both the defense and the prosecution agree to let the results be used in the trial. This decision must be made before the trial begins at a preliminary hearing or other type of formal meeting. Even if the defense and the prosecution agree to these terms, the results are subject to the presiding judge’s discretion. 

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