By: Anthony Harris, Latoya Ware, Amber Merritt, and Rashad Riley.

THE LIE DETECTOR The person’s breathing rate. The person’s pulse The person’s blood pressure The person’s perspiration; sometimes the polygraph will also record the leg and arm movement.  A polygraph is an instrument that simultaneously records changes in physiological processes such as heartbeat, blood pressure, respiration and electrical resistance (galvanic skin response or GSR). When the polygraph test is on a person, only four to six sensors are being attached to him/her. The sensors usually record:

How do the lie detector works  The questioner asks three or four simple questions to establish the norms for the person's signals. Throughout questioning, all of the person's signals are recorded on the moving paper.  Lie detector screen in blue  A polygraph examiner can look at the graphs and can see whether the vital signs changed significantly on any of the questions. In general, a significant change (such as a faster heart rate, higher blood pressure, increased perspiration) indicates that the person is lying.

John Larson, a University of California medical student, invented the modern lie detector (polygraph) in Used in police interrogation and investigation since 1924, the lie detector is still controversial among psychologists, and is not always judicially acceptable. The theory is that when a person lies, the lying causes a certain amount of stress that produces changes in several involuntary physiological reactions. History of the polygraph

U.S. Government studies have concluded that the single-issue (one question) polygraph exam, conducted properly by a qualified examiner, is 87 to 95 percent accurate. It is the most accurate tool available today for determining truth or deception. How accurate are polygraphs ( lie detector)

How does the test process work? a: The examiner receives and reviews the facts surrounding the case. b: The examiner explains the test process to the subject and reviews the case facts during the pretest interview. c: The examiner designs the specific test questions and reads each question to the subject to make sure each one is easily understood. d: The test subject is attached to the polygraph instrument and given additional instructions. e: The questions are read to the subject several times while he/she is attached to the polygraph sensors. f: After all charts (Polygraph) have been run, the examiner analyzes the charts and develops a numerical score for the test. This score results in a conclusion of either truthful, deceptive or inconclusive. g: The examiner will transmit the test results to the client verbally, usually within 24 hours. A written report may be requested, however some examiners will charge a small fee for this report.

Use of certain drugs and medications can also affect the exam, but such use generally results in an "inconclusive" test. It is virtually impossible to change a result from "deceptive" to "truthful" through the use of drugs or medications prior to an exam. If drugs are suspected, a pre-test (or post- test) drug screening is advised. Downfalls To a Polygraph