The Polygraph Unit has been conducting examinations since 1958. Examinations are conducted throughout the state on behalf of police, Sheriff's Departments, State's Attorneys, Public Defenders (mandated by statute), and courts. Preemployment examinations are conducted on all State Police applicants and many candidates for employment within municipal police and Sheriff's Departments.

The Polygraph Unit is used primarily as an investigative aid and provides technical assistance to any enforcement officer during ongoing investigations. The use of the polygraph in criminal investigation dramatically reduces investigative time and cost. The detection of deception technique eliminates truthful persons from suspicion and quickly identifies deceptive persons.