During the end pursuit, Garzah walks past a plump, dark-haired lady in a floral dress, pushing a baby in a stroller. As Donahue pursues in a following scene, he passes the same woman, now walking without her baby carriage and her left hand bandaged.
When the police and Mr. and Mrs. Batory at the waterfront, the sun goes up and then down.
Halloran gets his suit wet while walking past an open hydrant, but it is dried by the time he gets into the house.
When the two girls are in front of the dress shop looking inside, you can see Detective Halloran through the window speaking with a sales lady who is standing up. On the next immediate cut, which is an interior shot, the sales lady is now sitting down.
After being mauled by the police dog Garzah's left jacket arm is clearly raggedly torn, but his hand is unbloodied and still useful. It remains that way throughout the rest of his pursuit into the base of the Williamsburg Bridge tower. There he is shot by police in the left thigh. Ever after, however, his left hand is badly mangled, covered in blood, and functionally useless for even gripping a railing while climbing stairs.
As you look down 83rd Street in front of 52 West 83rd Street you see continuous city streets. This means no. 52 is on the north side. If it was properly on the south side (as all even-numbered New York City addresses are), you would see Central Park.
When Detective Halloran was chasing a suspect in the street, two people reacted as if they knew that Halloran was a cop. Halloran was in plain clothes, not displaying a badge and quite a distance behind the suspect; therefore, it would have been impossible for these people to know whether Halloran was a cop or just a plain person running to catch a train. However, given their timing it was reasonable to assume that Halloran was chasing the man that came by before him.
A half dozen or so police officers are around a police car in front of a large crowd of people. A gun shot is heard off screen and all the police look off to their left... while no one in the crowd turns their head.
When Detective Halloran was chasing the man who had just tried to kill Niles, a few people on the street pointed and yelled to the Detective which way the criminal went. However, there was one man who smiled directly at the camera and said something to the crew.
Moving the story into day two, the narrator says over what is supposed to be an early morning view of Lower Manhattan: "The city is quiet now, but will soon be pounding with activity." However, the shadows cast over the scene are from an afternoon sun in the west.
When the police visit Ed Garzah's work site, Ed is shown holding a small finish hammer (under 16 oz). Considering (by his pounding) he appears doing rough carpentry, evidently building concrete forms, he would be using a larger, heavier framing style hammer.
When Garzah is running along a street in New York, the car holding the camera (in the passenger window) is visible in the store windows, keeping pace with the actor as he stops and starts.
At one point during the chase at the end of the film, you could see the protective padding under Garzah's left jacket sleeve that was used to protect the actor's arm from the dog's attack.
When the two girls are in front of the dress shop looking at the window dummy model, a crew member can be seen through the glass reflection directing the background extras.
At 5 foot 3, Barry Fitzgerald was too short to be a policeman.