Excerpted from nolo.com post by Lisa Guerin

For decades, lie detectors, or polygraph tests, now more euphemistically referred to as “psychological stress evaluator tests,” which purport to measure the truthfulness of a person’s statements by tracking bodily functions such as blood pressure and perspiration, were routinely used on employees and job applicants.

Employers could—and often did—ask employees and applicants questions about extremely private matters, such as sexual preferences, toilet habits, and family finances, while a machine to which they were hooked passed judgment on the truthfulness of the answers. Push the machine’s needle too far by reacting to an offensive question and you could be labeled a liar and denied employment.

The federal Employee Polygraph Protection Act, passed in 1988, virtually outlawed using lie detectors in connection with employment. That law covers all private employers in interstate commerce, which includes just about every private company that uses a computer, the U.S. mail, or a telephone system to send messages to someone in another state.

The Employee Polygraph Protection Act allows polygraph tests to be used in connection with jobs in security and handling drugs or in investigating a specific theft or other suspected crime. However, before you can be required to take such a test as part of an investigation of an employment-related crime, you must be given a written notice, at least 48 hours before the test, stating that you are a suspect.

You can read the full story here.