Legal Definitions - polygraph

A polygraph, often referred to as a lie detector test, is a device used to monitor and record several involuntary physiological responses of a person while they answer a series of questions. These responses typically include changes in heart rate, blood pressure, breathing patterns, and skin conductivity (sweating).

The underlying theory is that deceptive answers will cause measurable physiological stress reactions. However, polygraphs do not directly detect lies; instead, they measure physical reactions that an operator interprets. Because the accuracy of polygraph results is highly debated and can be influenced by many factors, including the operator's interpretation, they are generally not admissible as evidence in United States courts. Despite this, law enforcement agencies and some government bodies may still use polygraphs as an investigative tool or for screening purposes.

Here are some examples of how a polygraph might be used:

• Criminal Investigation: Imagine detectives are investigating a high-profile burglary where a significant amount of valuables were stolen. They have a primary suspect who denies any involvement. To gather more information and potentially prompt a confession, the detectives might ask the suspect to voluntarily undergo a polygraph test. Even if the results suggest deception, they cannot be presented to a jury as proof of guilt, but they might guide further investigative steps, such as focusing on other evidence or interviewing different witnesses.

  This illustrates the polygraph's role as an investigative tool for law enforcement, helping to direct inquiries rather than providing definitive legal proof.

• Government Security Clearance: A civilian applying for a top-secret security clearance to work on classified defense projects might be required to take a polygraph examination as part of the extensive background check process. During the test, questions might cover past drug use, foreign contacts, or undisclosed criminal activities. The government uses these tests to assess a candidate's trustworthiness and suitability for access to sensitive information, even though the results are not considered infallible.

  This demonstrates the use of a polygraph in specific employment contexts, particularly those involving national security, where a high level of trust is required.

• Internal Corporate Inquiry: A large financial institution discovers a significant sum of money missing from a client account, and only a few employees had access to the relevant systems. To narrow down suspects and encourage transparency, the company's internal security team might offer a polygraph test to the employees with access. While the results wouldn't be used in a criminal court, they could influence the company's internal disciplinary actions or further investigations, potentially leading to an employee's termination or a referral to law enforcement.

  This example shows how a polygraph might be employed in a private, non-judicial setting to aid internal investigations and decision-making, separate from formal legal proceedings.