Visible crew/equipment: When Judge Dredd says: "Thanks for the heads up", you can see that the gun he is holding is a rubber stunt prop: you can tell because the front end is sealed shut when it should be open. Also, the barrel is thicker, certain details are missing, etc.
Dredd (2012)
1 visible crew/equipment mistake - chronological order
Directed by: Pete Travis
Starring: Lena Headey, Karl Urban, Olivia Thirlby, Andile Mngadi, Porteus Xandau, Rachel Wood
Continuity mistake: The homeless beggar at the entrance of Peach Trees gets splattered by the blast doors closing, creating a pool of blood on the ground. When they open again at the end of the film there is no blood or body.
Judge Dredd: In case you have forgotten, this block operates under the same rules as the rest of the city. Ma-Ma is not the law. I am the law.
More trivia for Dredd
Question: Why doesn't Kay kill Anderson after he grabs her and takes the elevator up to Ma-Ma? Or at least, why doesn't Ma-Ma kill her when Kay comes in with her? They were intent on killing the Judges and didn't care about the consequences. So what was Ma-Ma hoping to accomplish having her as a hostage that she couldn't try to accomplish without one? At this point, she already had the 4 crooked Judges on their way.
Answer: Kay wanted to punish her for what she did to him earlier. Ma-Ma wanted leverage against Dredd should he get past her Judges.
MasterOfAll