There have been several reviews of polygraph accuracy. They suggest that polygraphs are accurate between 80% and 90% of the time. This means polygraphs are far from foolproof, but better than the average person's ability to spot lies, which research suggests they can do around 55% of the time.

Can polygraph tests be wrong?

In other words, a polygraph test can sometimes be correct, and sometimes be wrong. Controlled lab studies have found that the tests are generally capable of correctly identifying a liar at rates greater than chance, but also incorrectly indicate that lots of honest people are lying too.

Can an innocent person fail a polygraph test?

The results of a lie detector test are unreliable, and many innocent people have failed them. Even if you pass the test, this does not mean that you will not be charged with committing a crime.