Polygraph Services

Detective Arguello conducts a polygraph examination 

In 1921, a student at the University of California invented the polygraph or "lie detector," and it has been used in police interrogation and investigation since 1924. A polygraph is an instrument that measures and records several physiological responses such as blood pressure, pulse, respiration, breathing rhythms, body temperature, and skin conductivity while the subject is asked to answer a series of questions.


During a polygraph examination, the person taking the test sits in a chair while the examiner hooks up several wire sensors to monitor physiological changes in the body.


You might imagine a machine with little needles that scribble on long scrolls of paper, but that is not the case today. Modern polygraphs use digital technology and the algorithms display on computer monitors. The trained polygraph examiner uses this data to discern whether the person is being deceptive.

William Marston engineered one of the earliest polygraphs, then went on to create the comic strip Wonder Woman, who used her magic lasso to force people to tell the truth. 

Sheriff's Detective Doug Cook trained for three months at Northwest Counter Drug Training Center in Pennsylvania. Following certification, examiners must follow stringent state requirements involving review of their work, continued training, and periodic testing in order to obtain a license, normally within two years.


Detective Cook administers polygraph examinations for our deputies and for local police departments that request services in connection with a criminal investigation. Local law enforcement agencies who wish to use the Sheriff's polygraph services may call Investigations at (503) 846-2500.