Polygraph Definition and Legal Meaning

On this page, you'll find the legal definition and meaning of Polygraph, written in plain English, along with examples of how it is used.

What is Polygraph?

n.It is a device or an instrument which is use to detect whether a person is speaking truth or not.It helps to find out the authencity of the statement given by a person.The test performd is called a lie detector test.

History and Definition of Polygraph

The polygraph, also known as the lie detector test, is a device that measures and records several physiological responses like blood pressure, pulse, and respiration while a person answers a series of questions. The polygraph machine is based on the idea that people's physiological responses will change measurably when they are lying compared to when they are telling the truth. It was invented in the early 20th century by John Augustus Larson, a physiologist from the University of California.

The polygraph has been used in law enforcement and intelligence agencies to identify deception in criminal cases, employment screening, and military investigations. However, its reliability has been questioned by some experts, and it is not admissible as evidence in court in many jurisdictions.

Examples of Polygraph

  1. In a criminal investigation, a detective administers a polygraph test to a suspect to determine if they are lying about their involvement in a crime.

  2. During a job interview for a sensitive government position, the applicant must undergo a polygraph test to determine their truthfulness.

  3. In a divorce case, one party requests that the other take a polygraph test to prove their innocence regarding allegations of infidelity.

Legal Terms Similar to Polygraph

  1. Voice Stress Analysis (VSA): a similar technique as the polygraph, but instead of measuring physiological responses, it uses changes in voice frequency to detect deception.

  2. Forensic Hypnosis: a method of interviewing witnesses and victims under hypnosis to retrieve more detailed information about crimes.

  3. Psychological Profiling: a method used to create a psychological profile of a suspect based on certain characteristics and behaviors.