In the scene where Chief Gillespie keeps Virgil at his house they appear to be drinking a bottle of Wild Turkey bourbon. When the Chief gets up and walks out of the room the bottle is not on the table. This occurs just after the Chief tells Mr. Tibbs that he doesn't want his pity.
When the sheriff is called to go and see the Mayor at his place of work Rod Steiger drives through Sparta and passes an elderly black gentlemen on the sidewalk . He is dressed in a shabby suit wearing a beige V-neck sweater and a hat. You then see the car drive a few hundred yards further into town and in the next shot, a few seconds later the same 'extra' is again walking along the sidewalk.
Sam apprehends Virgil at the train station and takes him to the Police Station. As they approach the entrance both the inside and outside doors are closed.The inside shot of them entering the station has only the screen door closed. The inside door is open.
During the shot where Sam Wood first approaches the train depot, he casts a very long shadow reaching behind him all the way up the building wall as if lighting is directly in front of him. In the next shot when he is passing the door and sees Virgil, the shadow has greatly shrunk down as if the lighting is directly overhead.
In Rod Steiger's first scene he is trying to get the air conditioner to blow harder in his office. He reaches up and gives the knob a good sized turn, only when his hand pulls back the knob is still in it's original position.
In the scenes where Harvey is being chased through the woods, there are shots that are supposed to be from Harvey's POV as he looks around the woods. If you look at the bottom of the screen where you're supposed to see Harvey's shadow, his shadow is that of the cameraman with the camera clearly mounted on the shoulder.
The town of Sparta is in east-central Mississippi. The Mississippi River forms the western border for most of that state. If Harvey Oberst (the fugitive being chased early in the film) made it as far as a bridge to Arkansas, he would have been at least 100 miles out of the jurisdiction of the Sparta police (who catch him). Even if, unbeknownst to the audience, the Sparta police had been deputized by some other jurisdiction, it's doubtful that they could have brought him back to the Sparta jail in the time frame presented.
Though the film takes place during a Mississippi summer, the exhaust of the patrol car can be seen briefly as condensed vapor as they drive up to Endicott's house. The only way this would be possible in the daytime is if the temperature outside was cold, which it was because the film was actually shot in Illinois during the fall.
At the start of the film as Saw Woods pulls away from the diner, you can see a car radio antenna on the right front fender of the patrol car. Yet Sam has a transistor radio hanging from the rearview mirror. Why would he need that if the car already has a radio? The tall antenna on the left rear fender is for the police two-way radio.
In the scene where Chief Gillespie brings Virgil Tibbs into the morgue, he (Virgil) starts examining the body without wearing gloves. It was established earlier Virgil is an "expert homicide detective" from Philadelphia (during the phone call between Chief Gillespie and Tibb's boss). As such, he would never do that.
The lyrics to the song Sam listens to on his transistor radio describe a bow-legged Polly and a knock-kneed Paul not being able to get together, yet anatomically these would in fact be ideal physical characteristics for a guy and a gal to "get together".
The goof items below may give away important plot points.
In the initial scenes shot in the Sparta police station, veteran character actor Peter Whitney is established as the policeman named Courtney. The interaction between characters Gillespie and Courtney throughout the film reinforces this, but near the end of the film, for whatever reason, an unexplainable shift in characters takes place. Right after the young girl, Deloris Purdy gives her account of her cemetery encounter with Officer Sam Woods and confirms that she is pregnant, Chief Gillespie calls out, "Courtney, you'd better get in here with a pad and a pencil..." Almost immediately, actor William Watson, who played Officer McNeil in the story enters the room ready to take notes... not the 'Courtney' we expected to see. (SPOILER ALERT) This info might not be appropriate to print as it gives away the 'who done it' conclusion of the story line: It happened once more at the conclusion of the confession scene when we see Ralph speaking into the tape recorder microphone held by Officer McNeil... "That's all... I didn't mean to kill him..." After a momentary pause, Chief Gillespie steps forward and says, "Yeah... alright Courtney, that's enough." How and why did William Watson become Courtney?
Delores' brother is shot and falls on his back. His body is in line with the car, his head near the driver's side front wheel. In the second shot his head is near the license plate. In the third shot his body has changed position and is perpendicular to the car parallel to the bumper.