Continuity mistake: When Atwater finds the gun in the box, it's sitting on lined notebook paper but when Voight looks in the box, the gun is now sitting on cardboard.
Factual error: Kevin sleeps overnight at woman's apartment. He doesn't share that he's a cop. The next morning in his unmarked police vehicle he uses his handheld radio that was appeared to be stored in the console and shows up on a violent scene with his weapon. It's obvious that Kevin used his official vehicle for personal reasons, and stored his radio and weapon in the vehicle unprotected overnight, which every police officer knows is wrong and a violation. (00:03:53 - 00:04:29)
Answer: Because he is a great cop and gets the job done better than anyone.