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)
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)
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)
Continuity mistake: When Vera reports the General's ominous phrase "He said the boat will never come", she's standing by the window - the leftmost window of the dining room, as visible later - but she wasn't there a moment before, when Quincannon and Armstrong were talking. (00:33:30)
Continuity mistake: Lombard on the cliff says "Mr Owen's hand is plain to see"; at the cut, the clouds in background are different, and the hat on Barry Fitzgerald's head adjusted itself - it was about to fly off in the previous shot. (00:32:10)
Continuity mistake: The men are looking down the cliff in search for possible hiding places. Blore asks the doctor if he OD'd the maid; he does it without a hand on his hat (he lowered earlier in the first shot) and then with the hand on it in the next shot. (00:31:50)
Continuity mistake: Vera approaches the General on the beach. He calls her "Juliet", mistaking her for his dead wife; during the close-up on June Duprez, the lighting is different and the foulard is windblown harder. (00:31:00)
Continuity mistake: Miss Emily Brent points her binoculars at the beach in the same shot when the men decide to start searching the island. She witnesses a brief exchange between Vera and the General, then follows Vera's movements who are in strict continuity. Merely a minute has passed, and the guys already are on the beach (which already can be quite a feat) discussing how their search was fruitless. They haven't searched a thing in so little time. (00:30:25)
Continuity mistake: Vera reaches on the beach Gen. Sir John Mandrake. When she exclaims "Sir John!" after he asked her (or rather, his dead wife) why does she love 'him', the sky is overcast and the shadows change radically in the next shot. (00:30:50)
Continuity mistake: In the scene with the various characters (Blore, the doctor, the judge) spying on each other, the keyholes the camera looks through are always perfectly lit, with none of the shadows the characters cast on the lock in the other views. (00:27:25)
Continuity mistake: Blore asks Lombard from the other side of the door "You mean you haven't any weapon?", hands off the handle. Hand on the handle in the shot that follows. (00:27:30)
