Polygraph Admissibility as Evidence in Utah Criminal Cases

Polygraph tests are used to determine whether a person is telling the truth or lying. The sight of a polygraph test is familiar because of various crime dramas and tv shows that portray the use of this device to catch criminals. However, Utah has not currently admitted the use of polygraphs in criminal cases to prove or disprove an offender’s innocence. If you or a family member is curious about the use of polygraph tests in criminal trials, you should speak with an experienced Salt Lake City criminal defense lawyer. With over 16 years of criminal law experience, Darwin Overson can help you with various criminal law issues. Overson Law is here to explain whether polygraph tests are admissible as evidence in Utah criminal cases.

How Does a Lie Detector Machine Work?

When you think about a lie detector test, you probably visualize a person asking questions while looking at a needle haphazardly drawing lines on a page. While this would not be an incorrect image to visualize, there some science to how a polygraph test is supposed to operate. Additionally, modern polygraph tests now employ the use of computers and other technology to increase accuracy instead of a needle on a paper feed.

A polygraph machine detects signals from a person’s body and translates those signals to a graph. When taking a polygraph test, a person has up to six sensors attached to their body to detect various signals:

  • The subject’s breathing rate
  • The subject’s pulse
  • Spikes in blood pressure
  • Increased perspiration by the subject
  • Any repeated movements (tapping your foot or fingers)

Before beginning the test, the questioner will typically ask a series of questions designed to document common “baseline” reactions and signals from the subject. Once the preliminary questions are done, the questioner will then ask the genuine questions and record the subject’s responses. The questioner can examine the responses given and determine whether the person’s vital signs were steady or spiking during a certain line of questioning.

Signs that a person may be lying include rapid and substantial changes in a person’s heart rate or blood pressure. Excessive sweating can also be an indication of lying.

When questioning about any kind of criminal act from drug distribution to rape, a polygraph examiner will likely use a method of questioning known as the control question test (CQT). A control question is a question that should be easy to answer and establishes a baseline. Then, questions designed to cause physiological responses are asked to get a sense of how the subject responds to stressful questions. This may include questions about past actions, such as, “Have you ever broken a promise to someone that trusted you?”

The responses to a CQT are then compared to relevant questions like “Did you commit murder?” or even a more focused question like “Did you kill your husband?” The reason for the comparison is for the examiner to trigger a lie with a control question that he can then compare to relevant questions for a possible signal match. Other common polygraph questions include:

  • Are you 35 years old?
  • Did you see who stole the drugs?
  • Were you born in 1956?
  • Did you steal the drugs?

Take note of how the above questions are intentionally meant to trigger a response. To learn more about lie detector tests, you should speak with an experienced Utah criminal lawyer.

Why Are Polygraph Tests Inadmissible in Criminal Court?

Polygraph tests are inadmissible in Utah criminal court because they are not reliable. The reactions that a polygraph tests for are not necessarily reactions to lying, but could be reactions to the stress of the questioning in general or even the temperature in the room. Every person’s reactions are different, meaning that it is difficult to provide concrete evidence of when a person is lying. Further, even trained polygraph examiners have to use subjective reasoning to determine whether a person is lying.

Utah had a series of court cases in the 1980s and 1990s that concluded that polygraph tests are not admissible in criminal court. The reasoning behind these cases was that no adequate scientific basis could be used to determine whether a person is lying. The court stated that division among the scientific community regarding the reliability of polygraphs shows that the test cannot be used as evidence. However, Utah courts have not completely ruled out the use of polygraphs in the future if technology can make them more accurate and reliable.

The Utah Rules of Evidence section 702 also prohibits the use of polygraphs in a criminal case. This rule states that for an expert in a particular field to testify about evidence from a test, the methods used in the test must be “reliable,” based on data, and “reliably applied.” In this case, experts do not agree that polygraphs meet the threshold to be relied upon in a criminal case.

Contact an Experienced Utah Criminal Attorney Today

If you would like more information regarding the admissibility of polygraph tests, you should speak with an experienced Utah criminal defense attorney today. Darwin Overson is ready to provide you with the legal representation that you deserve. To schedule a free legal consultation, call Overson Law at (801) 758-2287.