Plot hole: When the head of dept goes into the cold case vault and is murdered, the vault door closes behind her then she is locked inside, she is then attacked, the vault door then needs to be opened from the outside with the code. Meaning the killer would have to have been locked inside too.
Factual error: It is later revealed that Detective Banks partner faked his death by killing a meth-head junkie with the same tattoo as him. He included the junky's filleted skin with the same tattoo in a box with his badge to make it look like the other kills. Police, firefighters, first responders all provide DNA into a data bank to be identified in case something tragic happens and their remains are recovered. William Schenk's DNA would not have matched that of what was in the box.
Continuity mistake: SPOILERS: During the final scene, when Samuel L. Jackson is "puppeted" to lift his arm up to make it look like he's pointing a gun at the SWAT team, the number of laser-sights visible on his chest changes between cuts. In the wide-shot, there's only three, but when it punches into a close-up, suddenly there are five.