Factual error: In the scene where Lt. Exley arrives at the Night Owl after the murder, the patrol officer is wearing a Safariland velcro-fastened handcuff case on his left hip. That style of rounded cuff case was not introduced until the early to mid 70s.
Factual error: During the interrogation room scene, it is very bright in the room looking into the interrogation room, and it is dimmer inside the interrogation room. Although this would mean that the suspect would be able to see everyone watching as for him to just see a reflection, it needs to be bright his side, and darker the other side. True the glass could have been slightly reflective on one side, but the laws of optics still apply.