Ernst JÃ¼rgen: In the Stasi, we had a basic principle: ask enough questions and a man who is lying will eventually change his story. But the man who tells the truth cannot change his, however unlikely his story sounds.
After January Jones has just told Liam Neeson she doesn't recognise him. Neeson is trying to persuade Herr Strauss and two cops that he really is Dr Martin Harris of Langmore University, and suggests they look for a photo of him online. However, the cop using the computer says that it could take him ages to find a photo of Dr Martin Harris, as "there are more than 40 000 in the USA." This is very true, but as Neeson has already told him not only his name but also his place of work (Langmore university) in reality the cop would have found the photo far more quickly.
Throughout the movie if you look in the background at the various graffiti tags, one in particular stands out. Look for the tag OZ. In almost every scene that has graffiti on the walls you 'll see it somewhere in the background, sometimes more than once. Although it is common for graffiti artists to leave multiple marks in multiple areas, Berlin is a big city and it can be spotted too often for it to be coincidence.