Why did Mennick have a photo taken of Cassie kissing her roommates boyfriend before the murder? He didn't know about the roommate and her boyfriend yet, did he? He found out when he walked in on them and killed both of them.
Early in the movie there is a scene filmed at the WTC Plaza. This moves is 2007, 6 years after 9/11. Archival footage is way out of place. Later on there's a sky pan of NYC and the Twin Towers rightly gone.
When Cassie is taken to the boardwalk to be killed, all three of Mennick's henchmen get out of their vehicles (two from the limo, one from a trailing SUV). Yet, when the cops arrive, they wound one henchmen and kill a second. The third one is never seen again.
Mennick tells Cassie she was arrested at the scene with the murder weapon in her hand. However, the gun was actually on the floor of the murder scene and Cassie was found one floor below.