Those cops change every several hours. The murderer is all alone. For how many hours can a man stay awake and at the peak performance? In 20 more hours the police probably can walk into the apartment unopposed. There is absolutely no reason to force the issue, especially because the killer is needed alive for interrogation. (Probably they will just give him Sodium Pentothal and he will tell everything he knows.)
Thi is probably a Muslim neighborhood (No-Go Zone) where the cops are scared to death just to be there surrounded by tens of thousands of Muzzies. They don’t even want to go in with tear gas because it might set the hood off.