The suspect, Rego, after being shot twice, is put into the back of a police cruiser, without receiving any attention from the EMTs who are already there. He would have been transported, under guard, to a hospital.
The killer, Rego, who has been shot twice, is taken to the police station to meet with his sister. They are left alone in a room, with his hands cuffed in front of him. This violates every conceivable protocol for safety of the officers and civilians.
After kicking in the door of the Avenue D hotel room (without SWAT backup) Dylan, Lizzie, and Ryan just leave. Door still open, no one to secure the 'crime scene', no hotel staff to watch the room. Total violation of evidentiary procedure.
When Lizzie returns Ryan's gun to him, he racks the slide, then sets the pistol on the desk in front of him, instead of re-inserting the magazine and re-holstering the sidearm, thus preparing himself to use it should the need arise. Leaving a weapon lying out in plain sight is a gross violation of fire arms safety, especially among law enforcement personnel.