When Pizza Man is murdered, the crime scene is open to the public. Jonathan walks right into the apartment, the detective doesn't ask for his name and his business being there. Crime scenes are in fact meticulously preserved, officers stand outside letting no civilians in. On the scene, everyone allowed in wears protective suits. In the film. they are all dressed in regular street clothes only.
When telling the police about his intercom call, Jonathan says that he dialed the wrong number to accidentally reach the murderer, while in fact he called the correct number 333 for the apartment of his neighbor Hicks. So the phone number list near the intercom is flawed.