FORENSIC LIE DETECTION: THE POLYGRAPH TECHNIQUE
In order for a polygraph result to be accurate, the instrument must be in good working order; the examiner properly trained and experienced in question formulation and line chart interpretation; and the subject (examinee) a willing participant in the process. Not everyone is suited for polygraph testing. People who are ill, on drugs or alcohol, extremely obese, retarded, or mentally unbalanced should not be tested. The more serious the crime, the more reliable the results. It is important that the examiner be familiar with the details of the crime in question, otherwise he or she may not ask the most appropriate questions. The polygraph instrument measures and records the examinee's involuntary, physiological (bodily) responses to a set of ten yes or no questions. The examinee will know in advance what questions will be asked. Based upon changes in the examinee's blood pressure, heart rate, breathing patterns, and galvanic skin response, the examiner will draw conclusions whether, in response to the payload question - did you kill your uncle? - the subject is lying or telling the truth. Polygraph examiners are not recognized by the criminal courts as expert witnesses, therefore polygraph results are not admissible as evidence in criminal cases. A federal law passed in 1988 prohibits the use of the polygraph technique as a private sector pre-employment screening device. Most law enforcement agencies at all levels of government do test job candidates. It is a widely used investigative tool, and there are about a dozen polygraph schools in the United States.
Jim Fisher has extensively researched the history of forensic science. Presented here are selected, never before published articles written by Jim on the history of forensic lie detection using the polygraph technique.
The Polygraph Wars
In this tumultuous story of the birth of the modern polygraph, the two main characters are the man who invented the polygraph and the man whom history remembers as the father of the polygraph. Find out why they are not one in the same.
The Polygraph and the Frye Case
The 1922 murder trial of James Frye set the historical legal precedent regarding the admissibility of lie detection evidence in court. Read about the case and the trial here.
The Polygraph in the Lindbergh Case
What was the role of the polygraph in the investigation of the "Crime of the Century?" In this article Jim takes a look at the role of the polygraph in the Lindbergh case.