Polygraph testers generally ask many different types of questions, all of which the individual is able to answer with a "yes" or "no," such as questions about age. The test generally involves three phases: the pretest, testing and the post-test, according to the Polygraph Science Center. The examiner asks questions during the testing phase.
Testing involves certain questions to determine the individual's response under normal circumstances. Character questions, such as those involving the individual lying to someone he trusts, help to determine the individual's response when the test administrator asks a question requiring an answer where the truth is personally or socially unacceptable. Increases in blood pressure, pulse rate and perspiration, along with changes in breathing patterns, indicate the person being deceptive or telling a lie.
There are some areas where the law prevents the examiner from asking questions. The test should not include questions concerning religious or political affiliations or beliefs. It does not allow the examiner to ask questions concerning racial matters, sexual preference or lawful activities regarding labor organizations.
During the post-test phase, the examiner checks for signs of deception. If the test shows the subject was truthful in answering the questions, the test is over. If there are possible areas of deception, the examiner continues asking questions, giving the subject a chance to clarify his answers.