Robert De Niro had originally been cast in the role of CIA crime-scene operative Darius Jedburgh, but dropped out due to 'creative differences' after spending a few days on the set.
The movie marks the first time Mel Gibson has played the lead role in a film since Signs (2002).
The film underwent drastic re-shoots as the studio wanted at more action oriented film which caused the film's delayed release from it's original December 2009 slate to January 2010.
John Corigliano was the first composer on the project and wrote a full complete score to the original cut of the film with the National Philharmonic Orchestra in London with the legendary conductor 'Leonard Slaktin' conducting the music. When the film underwent re-shoots and the tone was changed to a more action driven film, Corgliano's score was then rejected as it did not fit the new version of the film. Howard Shore was then brought in by producer Graham King, who previously worked with Shore on The Departed (2006).