Post-Conviction Polygraph Examinations: Useful or Useless?

A polygraph exam attempts to measure “truthfulness” based on several physiological factors—such as changes in heart rate, breathing, sweating, and other physical responses. Ever since the polygraph exam was invented in 1921, however, it has been surrounded by heavy controversy. The largest controversy is whether or not polygraph exams are scientifically valid. Aside from debate over whether “truthfulness” can actually be scientifically measured, polygraph testing is vulnerable to factors like the skill level of the examiner, the IQ of the subject, the setting of the exam, and finally, the ability for subjects to employ “countermeasures.” Countermeasures include physical movements, mental exercises, drug use, and biofeedback training. In addition to these drawbacks, the polygraph exam is not admissible in court. Despite this, the polygraph can still serve other purposes—anywhere from assisting in the law enforcement hiring process to classifying the behavior of convicted sex offenders. Polygraph examinations may be administered at various points during a criminal investigation, both pre-conviction and post-conviction. For example, when a criminal investigation first begins, a subject may be polygraphed to be eliminated as a suspect. Once charges are filed against an individual for an offense, law enforcement may polygraph the subject to obtain more information. After conviction, an offender may be polygraphed at various points during their incarceration, as a part of research studies, as well as part of monitoring sex offenders. In the United States, more than thirty states require that polygraph exams be administered to monitor sex offenders. These periodic exams help track sexual offender’s therapeutic progress, identify risk factors, and shed light on any new offenses. This thesis paper provides a synthesis of the current state of literature surrounding the use of post-conviction polygraphs on sex offenders by outlining the numerous advantages and disadvantages.