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Why polygraphs are not admissible in court

On Behalf of | Oct 21, 2020 | Criminal Defense |

People arrested for serious crimes in Kentucky and other parts of the country are sometimes asked by police officers to take a polygraph test. These tests intend to identify which party is telling the truth when conflicting stories exist between a victim and an alleged suspect. However, the reality is not so simple.

How polygraph tests work

The purpose of the polygraph test is to measure changes in the heart rate, breathing, and perspiration of a person when asked certain questions. Sensors are attached to the chests, arms, and fingers of the person taking the test. These sensors monitor the physiological changes mentioned above. The presumption by lie detector test proponents is that a spike in any of these functions indicates nervousness, which, in turn, is a sign of deceptiveness.

However, criminal defense attorneys have been successful in disputing the results of lie detector tests, and no courts will acknowledge them as evidence of innocence or guilt.

The polygraph controversy

The problem is that a polygraph test is not able to measure the honesty of an answer given to a particular question. It measures the stress experienced by the person while answering.

The validity of a polygraph test is the subject of numerous hot debates. The American Polygraph Association proclaims a 90 percent rate of accuracy. However, a large number of psychologists are skeptical about the tests and say the rate of inaccuracy may be as high as 50 percent. Many police officers have also gone on record to dispute the validity of polygraph tests.

Opponents of polygraph tests say that in jurisdictions where the results of a polygraph are inadmissible as evidence in a courtroom, the test may become a tool used to bully people suspected of crimes into fully admissible confessions.

Individuals arrested for criminal offenses will need to defend themselves against the allegations to protect their freedom and good name. A criminal defense attorney is likely the best option for people needing to prepare themselves for their day in criminal court.