Continuity mistake: The survivors unlock the dining room after Rogers' death. The spare key lies on the tray with the Indians in a different position between shots; askew at first, facing the camera then. (00:54:50)
Continuity mistake: Blore, Lombard and Armstrong get out of the house to check on the knocking noise. As they stare at the door of the shed that keeps slamming in the wind, their reciprocal distance greatly varies; they are closely together, then Armstrong is at distance - to allow the camera to get a better shot -, then he is touching shoulders with Lombard. (00:52:30)
Continuity mistake: Blore gets up irate after Quincannon and Armstrong's confessions; the Judge next to him had both hands on the table, but he has just the right one in the new shot. (01:09:30)
Continuity mistake: Dinner after Quincannon and Armstrong bonded at the pool table. The Judge says "Very well, I shall begin." Blore is still using the cutlery on his plate, but he has both hands off the table at the cut. (01:08:25)
Continuity mistake: Blore is shaving. Suddenly something occurs to him and goes to the door calling Lombard. He has still bits of shaving cream all over his cheek; despite being still crouched by the door, after a brief cut to Lombard approaching, his face (in particular the sideburn who had still abundant cream on it) is practically clean. (00:58:00)
Continuity mistake: The judge looks with a certain apprehension at the doctor clutching menacingly his poker; he holds the pipe in both hands, but in the next shot both hands are at his sides on the couch. (00:46:15)
Continuity mistake: When Blore, Lombad and Armstrong come out of the backdoor and look at the shed from distance, the doctor's robe is tied with one end particularly long that sways in the wind and dangles at the very least touching the knee. After they see the hatchet and wood on the ground and begin bickering, both ends are roughly balanced and don't reach the knees. (00:52:40)
Continuity mistake: During the dinner scene with Rogers drunk, the Judge tries to bait him into confessing at least the original crime; the candelabra behind him project two shadows in different directions in the two waist shots. (00:44:35)
Continuity mistake: A drunk Rogers serves dinner to the guests; first one is the Judge, and at the cut the tilt of the serving dish changes significantly. (00:44:00)
Continuity mistake: The mixer is shown close when Dr. Armstrong 'turns down' the drink. It is full to the first horizontal notch, but when a few seconds later the judge reads his name because of the slip, the same bottle is in frame and about an inch emptier. (00:42:15)
Continuity mistake: When the secret vote is introduced, there's a small sketch with the doctor 'reluctantly' having a glass of liquor. He puts the glass down with the left hand, turned into the right hand at the cut. (00:42:15)
Audio problem: When Vera plays the piano, the Italian dub uses a different version of the song, with a much higher tempo and that does not sync well with the scene - plus, she'd have to be a world class pianist to execute it that way. (00:40:00)
Continuity mistake: With 7 balls left, the Judge tosses only 5 in the pool pocket, but only one remains on the table. (00:38:55)
Continuity mistake: During the demonstration with the billiard balls as 'Indians', the balls are placed differently on the table depending on the take. (00:37:00)
Continuity mistake: During the conversation by the pool table, The Judge explains it's a "game of the mind"; the doctor is leaning against the table with his left arm in front, but his pose changes at the cut, when his right arm is off the cue stick and the one he is using for support. (00:37:10)
Continuity mistake: Vera is looking outside the window before Lombard plays the piano; she has one hand against the glass, but the arms are low down her body in the next shot. (00:36:10)
Continuity mistake: When the Judge sets up his reveal that Mr. Owens must be one of the guests, look at the shot of the whole room; Blore is leaning with both one arm and both hands on the armchair, and Dr. Armstrong is holding the knife in one hand. This is the same way everyone will look in the last shot of the scene too. Any other dramatic shot in between, with Blore initially with both hands on the table, or Dr. Armstrong holding the knife in two hands, and even the butler counting with the aid of his fingers instead of keeping the fists clenched, is moot. (00:35:00)
Continuity mistake: After the General's murder, Thomas Rogers calls the doctor and announces that there's another figurine missing. In close-up, Richard Haydn's hand is on his chest, while he has both down his sides in the shots of the whole room. (00:34:30)
Revealing mistake: Rain is pouring on the windows, but when Lombard comes back with the bad news about the General, he's in pristine condition. (00:33:50)
Continuity mistake: Blore and Lombard are watching outside during the storm, with everyone inside the house but general Mandrake. From the outside looking in, Lombard is only partially in the window, and Blore is turned sideways. Indoor shot; Blore is facing the window frontally, and Lombard is all the way visible, perhaps just a part of his foot would be obscured by the curtains. (00:32:25)
