Continuity mistake: When Helen grabs the bottle of hot sauce from Blanc's hand, the label turned between shots and it begins in Blanc's right hand when he was just switching it to the left in the previous shot. (01:45:15)
Continuity mistake: In the flashback, "Andi" is dead with her right arm on the last step in most shots (as she was the first time we saw the scene) or the one below (like when Blanc is crouching and curses saying "Sh*tballs." (01:45:20)
Audio problem: The second time we hear everyone reacting to Andi's death, the timing of the lines is different and Edward Norton says "God, Andi." (01:46:00)
Continuity mistake: When Helen reveals herself holding the envelope on the stairs, she holds it with one, then two hands in the two separate shots. (01:52:00)
Character mistake: During the dénouement, Benoit Blanc starts "That night, Lionel faxed Andi's email to Miles." But it's established that he faxed it minutes after receiving the mail, which was sent at 4 pm. 4 pm in May, that's hardly 'night'. And it can't be night where Lionel is, since he shows up a little later together with Claire, from Connecticut, at the house of the victim in the New York area. (01:52:25)
Plot hole: It's an established fact that the culprit is an idiot (actual quote), but still, not a COMPLETE idiot. Some things such as keeping the envelope as some sort of trophy are in line with the hubris of villains, but there's absolutely no reason at all why he would still have in the back pocket of his pants Duke's phone after having a ton of time to get rid of it (he got rid of the gun and a pair of gloves he had the time to go look for in the dark too), especially in a spot so visible and being known for not owning any phone himself. (01:53:40)
Other mistake: In the close-up of the article about Andi's death (the second time we see it, during the denouement, since the first time when Helen sees it the framing is too tight to notice), her full name (Cassandra) is misspelled in the body of the article ("Casandra"). It also mentions her sister Helen; if her identity is so well known and accessible, considering how high profile the trial was, it's borderline insane that nobody would know about her; the media would have been all over her. (01:54:00)
Other mistake: In the original version and in the flashback, Benoit Blanc's delivers the lines about the "loaded gun on the table" in a different way and gestures differently throughout it. (01:56:10)
Continuity mistake: When Helen shows in close-up Andi's napkin for the first time, look at the position of her finger, next to "Teaching." After a brief cutaway, it changes position. (01:57:05)
Other mistake: During the first part of the movie, the Mona Lisa shield is triggered by all sorts of acute sound; phone alerts, speaking too loudly. Somehow it is also never released (one wonders how can it detect when the threat is over). At any rate, after the gag has run its course, in the third act the protection is not triggered anymore except when the plot makes it convenient (the lighter). (01:57:40)
Continuity mistake: Helen pleads someone to say "I saw the napkin before he burned it." In the background, Miles is standing, hands down his sides. The camera cuts awa a split second on Claire and Lionel, and then there's a close-up of Edward Norton leaning with the back, and the palms of his hands, against the table. Same few moments later. (02:00:10)
Continuity mistake: When Blanc "offers some courage" to Helen, his hand in close-up is around the side of the glass, and it is above it at the cut. She accepts the glass, and her hand changes position on it at the next cut as well. (02:01:05)
Continuity mistake: When Lionel says "Why the hell not?" at the unspoken understanding of starting to shatter statuettes, Claire next to him is standing clawing at her own fingers, while in the background a moment earlier her hands were higher and distant. (02:02:30)
Continuity mistake: When Helen is bashing the bar, the gestures of the other characters in the background are inconsistent from shot to shot (just look at Kate Hudson and Kathryn Hahn's reaction shots, for instance). Same when a few seconds later she throws pillows in the fire. (02:04:00)
Continuity mistake: In the close-up of Helen igniting the alcohol on the floor, she moves the arm away from the floor and all the way out of frame, appearing also to get up from her kneeling position. A few seconds later in the wider view of the room she is still with her hand down. (02:04:15)
Continuity mistake: The bloodstains on Helen's top change midway through the ending. For instance, when she walks towards Miles after smashing most of the glass sculptures to eventually show him her trump card, she has a visible red spot on her right breast (which you could see earlier even when she was wearing her blazer), gone when she gets up from the floor after the explosion. (02:05:00)
Continuity mistake: When towards the end of the movie Miles from the top of the stairs shouts "What? You think you're an alligator?" Birdie and Whiskey are in a different position in their close-up. (02:08:30)
Audio problem: Helen reminds Miles the line he used "To forever be remembered in the same breath as the Mona Lisa." The line is said in the span of a couple different angles; when she says the word "in the same", the camera is behind her, and you can see that her jaw is not moving. (02:09:15)
Continuity mistake: Miles tries to rally the troops after Helen delivered the line about him being ruined. He calls out "Gang?" Lionel is staring into space facing away from him, then in close-up he is still staring into space, but turned more towards him. (02:09:40)
Continuity mistake: Lionel states that he saw Miles drive away with his right hand raised, left hand in the close-up. (02:10:00)
