If nobody watched them, how do we know they slept through their shift, and if they did, how do we know they did it because they were tired and not because somebody asked them to sleep for a while and not worry about a thing, and that part of overtime would be paid at much, much different rate?

> I doubt they've even been fired.

Especially in this situation. We have huge motive, excellent opportunity and unless one of the guards is so stupid as to talk, almost no possibility of detection. A perfect crime, if there's one. Of course, there's no proof of that - maybe Epstein indeed was suicidal. Maybe the guards were just paid to give him an opportunity, not avoid witnessing murder. Who knows. But I don't see how guards sleeping excludes any of that.