They all do, a polypraph is absolute bullshit. Even the dude that invented it said he regretted it because it doesn't work and people were putting too much faith in them. Really a polygraph tested under scientific conditions is accurate 55% of the time. Which is no more accurate than randomly guessing true or false. The whole thing is an ingeretation tactic because a lot of people are dumb enough to believe it can 100% tell you are lying. Like the guy said some people believe it so much that they just confess before even taking the test. It's just like a tool to use to crack someone. Its basically like robbing someone with a toy gun, thebgun doesn't do anything but they dont know that and are going to hand over the money.
Lie detectors are known to be faulty and not accurate at all. This guys gonna try to convince people otherwise because his career but they're known to be faulty as eye witness reports. You can remeber false memories you can also convince yourself of things that aren't true.