@Siren_six My advice: don't trust, verify.
In theory a great way to do that could be to have someone else pump him full of sodium pentothal, then have them (while his inhibitions are shot to shit from that) do everything they can to irritate the hell out of him.
If he reacts badly, you know the only things standing between him & shit behaviour are a few inhibitions - best to steer clear.
If he's good-natured about it, you MIGHT have found a good one.
Unfortunately not practical/legal in RL 😦
@IrelandTorin I wish I had access to these kinds of chemicals but sadly I don’t.