Which U.S. law prohibits most employers from using lie-detector tests on employees?

The Employee Polygraph Protection Act generally prohibits most private employers from requiring or requesting lie-detector tests for employees or job applicants.

Congress passed the law in 1988. It covers most private employers but contains narrow exceptions, including certain security-service, pharmaceutical, and controlled-substance employers, as well as investigations involving economic loss or injury when specific conditions are met.

The act also restricts employers from dismissing, disciplining, discriminating against, or threatening workers because they refused a prohibited test. Employers that lawfully use polygraph examinations must follow notice, qualification, and procedural requirements.

The law does not cover every workplace equally. Federal, state, and local governments are generally outside its main private-employer framework, and other laws may impose additional limits. The Department of Labor’s Wage and Hour Division enforces the statute.