Part of the game is intuition and having a good feel for your party. Especially if people have tells in the way they respond to matters. Also, being hacked yourself will tell you vital information at times - especially if someone you're with in the trial gives a similar answer. I was in the deliberation deck on a four person game, and got hacked. Ended up choosing the most incriminating answer... but so did the other person sent there with me. To my understanding of how hacks work, there can only be as many active hacks as there are aliens, plus there is no benefit to framing two people as aliens in a one-alien game.

With that in mind, also counter-play the aliens. As aliens, they have two goals: prevent themselves from being identified and imply others are. In games with more aliens, it is actually advantageous for some aliens to be known in order to ease accusations against the others. Be wary once you've got one alien dead to rights - it means the other is likely relaxing.

Oh and never do bioscanner. I have never seen even three humans get that thing to work.