The hostages at the start of the film
I'm sure this has been brought up several times by now. But through forensics, especially, the way it should have been more advanced, since it was set 2 yrs in the future from the time the movie was released, the police should have been able to figure out that the hostages were already dead once the building exploded- making Spartan's arrest and sentencing unnecessary. Of course, this is just one of the many mistakes they made in this film. But, this should have been the most obvious and should have been corrected before it's release. (and I've already acknowledged that his has probably already mentioned. This is just an observation. So please, no comments saying "duh" or "no *beep*" or anything like that lol)
"In the pursuit of truth there are many doors to deception.Open your mind.But, guard your heart"-me