When the killer shoots the shotgun through the door, the hole is jagged and oddly shaped, as it would be. Later, when the detectives are at the crime scene, the hole is perfectly round with smooth edges.
In the opening scene, Murray the Junkman is seen holding the bag of heroin before Sharky hands it to him.
Watch the locomotives pulling the train in the open scenes. Sometimes they're F.E.C. (Florida East Coast R.R.) locomotives and at other times they're Family Lines/Seaboard Coast Line/CSX. These are two separate rail lines to Miami that run parallel to each other but are a few miles apart. Much of the opening scene footage, however, seems to have been shot along the CSX (ex-Family Lines, ex-Seaboard Coast Line, ex-Seaboard Air Line) track.
On the boat when Sharkey overpowers Smiley, the gun in Smiley's belt is clearly an automatic, but when Sharkey shoots out the light in the room and kills the incoming Asian hit man, the gun has switched to revolver.
After Arch climbs over Papa's dead body on the stairwell, Papa moves his head.
The license plates on Murray's car and the senator's car both simply say "Bicentennial" across the top with "81-82". All Georgian license plates at that time had Georgia written on them.
When Billy Score shoots his first victims his gun has a silencer mounted on the barrel. We still hear "boom, boom" anyway. One shot is even heard from a POV outside the apartment where the killings are occurring.
A crew member holding a clapper board with a reflector behind him is visible in the car door window just as the Chins speed from the curb to run over Jo Jo.
On the boat, Smiley tells Sharky, "When you went to see the man, you really pissed him off... you should have just turned[Dominoe] in. She'd be dead, but Nosh, Jo Jo and all your friends would be alive." But the way the movie is edited, Nosh and Jo Jo were killed before Sharkey went to see Victor to tell him Dominoe is still alive.
In the end scene when Sharky is approaching the window.
When the crime lab is analyzing the drug found in the hotel room, the computer readout misspells dilaudid as "dilawdid".
They define "dilawdid" as "Synthetic Heroin" whereas "Dilaudid" is Synthetic Morphine.