The Polygraph

The Polygraph

What is Forensic Psycho-physiology?

The word “forensic” refers to the use of scientific knowledge or methods in solving crimes. “Psycho-physiology” is a branch of psychology which is concerned with the physiological bases of psychological processes. In other words, it is the study of how the mind interfaces with the body. When a person is under some form of psychological stress, there is a resultant effect on the body. The “flight or flight” response is an example. When the mind perceives a threat to the well being of the organism, certain changes occur as a result of arousal of the Sympathetic Nervous System; the pupils dilate to allow better vision in low light, the palms of the hands become sweaty for better grasping of objects, heart rate and blood pressure may increase, as well as respiration to allow faster transfer of oxygen etc. These are involuntary responses that have evolved within us to deal with a perceived threat.

These physiological changes can be monitored and measured with specially designed sensors attached to the body. Polygraphy is a subset of psycho-physiology, which attempts to measure and relate these involuntary reactions to deception or lying. Most people have been programmed since childhood to know that telling a lie is inappropriate behavior. When we lie, our bodies will exhibit some or all of the aforementioned involuntary responses. An expert in polygraphy can analyze the magnitude of these responses in relation to normal baseline responses and determine if someone has been truthful in response to a question (stimulus), which the guilty person can perceive as a threat to his well-being.

What is the Polygraph?

The Polygraph, also referred to as a “Lie Detector”, measures and records several physiological parameters such as blood pressure, pulse, respiration, and skin conductivity while the subject answers a series of previously reviewed questions. The “Polygraph Technique” provides the concept that that deceptive answers will produce physiological responses diverse from those associated with non-deceptive answers. In some countries the polygraph is used as an interrogation tool with criminal suspects or candidates for sensitive public or private sector employment. US law enforcement and federal government agencies such as the FBI and the CIA and many police departments such as the Los Angeles Police Department use polygraph examinations to interrogate suspects and screen new employees.

How is the Polygraph Exam Accomplished?

Polygraph examiners typically begin polygraph test sessions with a pre-test interview to obtain some preliminary information, which will later be utilized to develop diagnostic questions. At this time, the examiner explains to the subject how the polygraph works and how the sensors will be attached. The examiner then reviews all the questions with the subject. Once the subject is comfortable and ready to proceed, the sensors will be attached and adjusted, then the questions will be asked in series, which is repeated 3 to 4 times with a short pause in between. Depending on the results, the examiner may run an additional series. On rare occasions, it may be required to accomplish follow-up testing after a period of rest. The results and formal report will be made available within 24 hours as we have a strict quality control policy that includes a peer review.

Uses of the Polygraph