That's not as accurate as flipping a coin. It's a certain success or a probabilistic failure. A random coin flip could get you the wrong answer either way. But here, if someone confesses to something, you can be sure it's true. (unless you pass the threshold where people would rather lie that they did bad things, but that's a different problem... if you're getting the same results as torture, the interviewer is the problem, not the fake machine)