I've found the eye witness, but now I can't do anything. elevators don't work and all the other doors are locked.
I'm assuming that this is trainer related and that you are running the legal Version of the game.
If so then this is what I've experienced;
The Freeze game Timers(F9) and Invisible mode (/) tend to prevent the game from progressing during certain missions, try deactivating those two and the game should progress properly.