In instances where lie detector tests have been used to induce a suspect into making a confession, there have been a high number of false confessions.
In Chicago in 2013, Chicago police began unofficially and illegally using polygraph tests to induce confessions from suspects. Only a small percentage of the test results were even recorded, as the results were not important. Instead, the police officers told the suspects that they had failed a polygraph test, even when they didn’t, in an attempt to obtain a full confession.
When the suspects were repeatedly told they had failed the lie detector tests, some offered false confessions in the hope that the interrogation would end. ISome of these suspects ended up spending years in prison before DNA evidence later exonerated them and secured their release. 
Younger suspects, those taking the test in their second language and those with mental disabilities were most at risk of providing a false confession when confronted with a lie detector test. However, anybody, when subjected to more than 50 hours of aggressive interrogation techniques without sleep, may find themselves sufficiently pressured into giving a false confession.
Using lie detectors to obtain a confession effectively amounts to getting the victim to provide a confession under duress, and should not be admissible in court.