Lie detector is a device that helps determine whether a person is telling thetruth. A lie detector, also called a polygraph, records physical changes that occur  16   questions. Such changes include alterations in the blood pressure, pulse   17   , perspiration (出汗), and respiration (呼吸)that may occur when an individual lies. It helps police and other     18  question suspects about their possible involvement in a   19    .Polygraph experts and other supporters of lie detector testing believe that such tests are highly accurate. Some criminal cases are decided on the basis of lie detector tests,   20    can be used as evidence if all people  21  agree beforehand to their use. A person who agrees to do so is connected to a polygraph and sits in a chair while answering questions. The lie detector makes a continuous    22  of body functions by drawing lines on a moving graph. Some of the questions asked during a lie detector test arc related     23   the matter being investigated. Others are unrelated or only    24     related, but they are included to improve the test’s   25   . Each question must be answered yes or no. If a person lies, the graph normally records a physical change. This change occurs because of the person’s   26   response to telling a lie. After the test, a lie detector examiner    27  the test results.But many legal experts believe that testimony obtained with the aid of lie detectors is not accurate enough to be used     28     . These experts also say that such testimony may    29  the legal principle which can protect people     30   testifying against themselves. The judges in most criminal cases do not permit testimony obtained with lie detectors to be used as evidence.

16()