@Disguised22
since 1903
its pretty complicated but long story short, to lie your brain need to actively think up an imagined scenario, as the brain dont remember the lie happening.
the drug prevents you from "thinking" more complex thoughts making it harder to lie and makes you more vulnerable to being pressured.
so the theory is that when you cant imagine a fake cenario the only thing you can do in that situation is to "recollect" what have already happened.
thus making you unable to lie, basiclly a stronger version of hypnosis. ( the real kind, not the mind controll mumbo jumbo )
the problem is that while it worked, it was never 100% reliable for a few reasons witch iis why if it was used in a interrogation today it would not hold up in a court.
But if you are interested go a quick google on eather and truth serum and it should get you covered.
its a pretty popular piece of history because it was actively used in both world war 1 and 2.