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Writer's pictureMark Linton

Polygraph Exams and Lie Detectors in Criminal Cases.

Updated: Nov 18



A polygraph test or lie detector is a valuable tool for criminal cases. Polygraph exam results are not admissible evidence for purposes of a preliminary exam or a trial. However, you can utilize the results in several other ways to assist the defense in a criminal case.


I use successful polygraph exam reports for 6,500 motions. These help individuals overturn a criminal conviction after they complete the appeals process.


Law enforcement often utilize polygraph exams when investigating crimes to determine if a suspect is being honest with their responses to investigator questions. Law enforcement cannot compel a defendant to take a polygraph exam due to the protections of the 5th and 14th Amendments. If an exam is conducted, the results are not admissible at a trial. In addition, a jury is not allowed to even hear that a defendant submitted to a polygraph exam or was willing to take an exam to clear their name.


I will often have a client take a private polygraph exam from a trusted examiner. Unfortunately, a lot of times they do not pass the private polygraph exam, so I will not subject the client to a police polygraph exam. The benefit of using a private polygraph exam being if the person does fail, nobody other than the attorney, client and the private examiner knows the results.


However, the results of a police exam can impact the decisions of an investigator and prosecutorial decisions. When submitting to a police polygraph exam, it is important to know that anything the defendant states during the exam can be used as evidence against them. So, if the defendant makes some kind of admission or confession, the examiner can be called to testify.


The tricky part is that a defendant is entitled to have their attorney present during a police polygraph exam. However, the police will often refuse to administer the test if the attorney is present and will insist on the defendant signing a waiver of this right. As a result, a police polygraph exam is a law enforcement tool to try and interrogate a defendant and gain evidence for the case without violating their Miranda Rights.


Criminal sexual conduct cases are where polygraph exams are the most utilized. In Michigan, a case for criminal sexual conduct can be prosecuted solely on an alleged victim’s statement, without any corroborating evidence. I’ve seen cases where there is no physical evidence, medical evidence, no other corroborating witnesses and the defendant was convicted of criminal sexual conduct. In this scenario, it basically comes down to whether the victim or defendant performs better during their testimony, which is a scary proposition given the sentence can be for life.


A criminal defendant is legally allowed to demand a police polygraph exam if they are charged with criminal sexual conduct. Ironically, Michigan law prohibits law enforcement from requesting or even offering an alleged victim a polygraph exam. However, if the defendant passes the polygraph exam, law enforcement is required to notify the victim of the result. Based on this information, law enforcement may give an alleged victim a polygraph exam only if the victim makes the request to take an exam.


What happens if a defendant passes the police polygraph exam? I’ve experienced mixed results. I’ve had prosecutors agree to dismiss first degree criminal sexual conduct cases. I’ve also had prosecutors take the position that they do not care about the results, and the case will go forward as charged.


What other ways can a polygraph exam result be utilized? It can be used for a motion to suppress evidence, a motion for a new trial and for a 6500 Motion. It can also prove useful when the court sentences the defendant.


If you need of an experienced criminal appellate attorney for an appeal or 6500 Motion, call Mark Linton for a free consultation.

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