Well, I've never played the game... and again, this game is mostly played by people younger than me, so the inexact word "proof" is probably fine for most players.
But I will say that another useful tactic (whether it's in a game of among us or in a police station) is saying as little as possible... of course people who don't talk are sus, so what you can do is keep asking things like "explain it to me" over and over (or something similar). It would simultaneously put the onus of talking on them, while creating the illusion that you're earnestly interested in brining more facts to light.
Any tips if you are imposter?
Then when there's a lul, use the sneaky word "because"
So "explain it to me" and after they take a pause, start your next sentence with the word "because" and then again end with "explain it to me"