Just to clarify, what exactly do you mean by staged screenshots? If you are talking about users who photoshop chatlogs to alter their meaning - by extension the same users could photoshop a timestamp? Or am I misunderstanding the scenario you're describing?
In any case faked screenshots are usually painfully transparent.
I believe staff keeps logs of everything that is said in toribash so if its really that important, they could just check those.
Unless im just imagining that and im actually dumb.