A polygraph examination, commonly referred to as a lie detector test, is often used by law enforcement for a variety of reasons. However, the results of a polygraph are not admissible in Michigan courts as evidence because it does not meet the scientific standards for reliability (most studies put polygraph accuracy at about 90%). However, it is extremely important to remember that even though the polygraph results are not admissible, any statements you make during a polygraph can be admitted as an admission.
How Does a Polygraph Work
A polygraph is supposed to detect when a person is lying by recording the suspects’ bodily reactions to questions. Polygraphs are based on the premise that a person’s body will respond in certain ways when they are lying. Four to six sensors are placed on the suspects’ body which measure: pulse, breathing rate, blood pressure, perspiration, and body movements. The readings are recorded by ink on a moving piece of paper by computer.
Typically, a polygraph will begin with a pre-test interview to gain preliminary information to develop possible test questions and build rapport with the suspect. The suspect will be asked to sign a sheet containing Miranda rights indicating that submitting to the polygraph is knowing and voluntary.
Establishing a Baseline for the Polygraph
A baseline is established by the person conducting the polygraph to calibrate the equipment to the body chemistry of the suspect. During this portion the suspect will be asked to deliberately lie to the question being posed by the examiner (polygraphist) to see if he can detect a lie. When the real test begins about four or five questions relevant to the issue at hand are asked. Sometimes control questions will be mixed in with the other questions to measure any changes between the control questions and relevant questions so that a change in response can be read by the examiner. The polygraph examiner looks at changes in the readings to determine if the suspect is lying. The reading is subjective by the polygraphist which is one of the reasons why lie detector tests are not foolproof.
The polygraph concludes with a post-test interview. If the examiner believes the suspect is lying he will often try to elicit a confession. It is very important to make no admissions during or after a polygraph. If a suspect is told they have failed the polygraph, make no more statements or volunteer any statements.
Never Take a Polygraph Without First Consulting with an Attorney
No one should ever take or agree to take a polygraph without first consulting with an experienced criminal defense lawyer. The police polygraphists are not there to help you or clear your name. They are trained to get confessions or trick you into confessing despite how friendly they may act. Some polygraph examiners will go beyond the scope of the relevant issues when administering the polygraph. No matter what they tell you, they are not on your side. I never have a client take a polygraph without first arranging a private polygraph to see how the client performs. There are many legitimate reasons why someone will not pass or do well on a polygraph. They are just not reliable enough.
Advantages and Disadvantages of Taking a Polygraph
The advantage of a client passing a private polygraph is that it can be used to persuade a prosecutor to drop charges, particularly if the evidence is weak or it is a “bare bones” case. If a client can pass a private polygraph I am usually confident they can pass one administered by the police. The disadvantage of failing is that if the prosecutor had any doubts at all, they will probably be fervently convinced and press forward with the case. Family and friends may no longer offer their emotional and financial support. However, the results of a private polygraph arranged by your criminal defense attorney should not be shared because it is strictly confidential. The disadvantage of a police polygraph is that any confessions made before, during, or after can be introduced as evidence at trial.
Polygraphs in Sex Crime Cases
If charged with certain sex crimes, you may be entitled to have a polygraph exam be administered. This is especially true in cases where the defendant maintains his innocence and the medical reports do not support the complaining witness’s story. Again, that decision should not be made without consulting with an experienced criminal defense attorney.
Michigan Criminal Defense Attorney
If you have been charged with a crime or are under investigation, do not make any statements to the police or agree to take a polygraph without first consulting with an experienced criminal defense attorney. Call Austin Legal Services, PLC at (517) 614-1983 for a free no obligation consultation today!
Defending criminal charges throughout Michigan in the counties of Ingham, Eaton, Clinton, Livingston, Jackson, Gratiot, Calhoun, Kent, Barry in the cities of Lansing, East Lansing, Mason, Jackson, Brighton, Howell, Grand Rapids, St. Johns, Ithaca, Hastings.