As with the previous 2 interrogation trophies, this one is un-missable as well. You will obtain this during the third mission of the DLC.
Well over halfway through the mission (you will have went through the pitch-black warehouse and cleared out a huge open area that has derailed trains and such) your main objective will be to interrogate a guy named Ulianov. Before doing so you will clear out a whole outpost. There are a few snipers in elevated positions and many patrolling ground troops. Once all threats are eliminated, proceed to the target building and once you enter you will be thrown into another cutscene.
At the end of the cutscene/interrogation you will unlock this trophy.