Character mistake: Catherine Dent's character, Kay Marquette, plays the Holmes character Irene Adler with an English accent. Adler was an American, as mentioned by Watson in "A Scandal in Bohemia".
Continuity mistake: When the fannysmackers attack Greg, they smash his car back window out. The next morning, when Warrick and Nick are processing the scene, Greg's car window is completely intact.
Revealing mistake: When Nick is in the shed in the desert, sunlight is coming in through hundreds of holes in the walls and roof. Since the sun is in one spot, all beams of light should be in the general same direction. In this scene they come from at least 5 different directions, with some originating from a light source very close to the outer wall (causing beams in a radial pattern).
Getting Off - S4-E16
Revealing mistake: When Sarah and Catherine are looking over the body of the dead clown, in one scene his eye flutters and in the next he distinctly takes a breath.
Continuity mistake: In the opening scene, the female student is wearing green panties. When the two bodies are found, she is wearing red panties. It was a murder behind a locked door, so no one changed them for her.
Suggested correction: The girl had green panties with pink or red strings. When she was found, all that was visible was the string.
Continuity mistake: In the scene just after Hodges and Greg find the seafood they were hunting for in the "Pleasure Providers'" stations or whatnot, Hodges collects a sample of the shrimp by cutting off a little piece. He picks it up with his fingers. In the very next frame, the shrimp piece is in tweezers. Lightning speed. (00:30:55)
Continuity mistake: Stephanie Watson's supposed killer is, on the TV, named as Mark Kelso, but later when Catherine is going over the DNA sample with Greg, it is a match to a Dwight Kelso - supposedly the same person.
Revealing mistake: At the end of the episode when they view flashbacks of what happened when Zack died, there is a scene when Tyler is performing CPR on Zack. You can see that Zack is a dummy. (00:39:55)
Revealing mistake: The elements of the miniature crime scene are not glued. They should not be in their respective locations, but all over the floor of the miniature.
Other mistake: Despite the city-wide outage from the storm, there's quite a visible glow around the house as Sarah and Nick investigate the grounds, that isn't moonlight.
Suggested correction: A personal generator? Or (more likely) a generator from the CSI gear?
Targets of Obsession - S11-E15
Continuity mistake: When Justin Bieber gets shot, we see him from the back as he falls back, and his left hand is flailing around with no gun in it. We then cut to him from the front falling backwards, and he's holding the gun in his left hand the whole way down to the ground.
Other mistake: Season 10, episode 4 "Coup de Grace": When Nick is doing the phenolphthalein test on the q-tip, it turns pink immediately and starts to overflow pink coloring all the way down the side of the stick, which is not how that test works. Normally it takes a few seconds and only turns color around where the blood is.
19 Down (1) - S9-E9
Factual error: Season 9, Episode 9 - 19, "Down": Towards the end of the episode they are searching along railroad tracks. A MetroLink train passes by. MetroLink serves the greater Los Angeles area, but does not serve Las Vegas.
A Kiss Before Frying - S11-E12
Continuity mistake: Near the end when Greg meets Rita at the bus station, she puts her arms around his neck. The next shot from the front shows her arms and hands on Greg's chest. Rita's arm/hand position changes continually throughout the scene.
Disarmed and Dangerous - S9-E12
Plot hole: Series 9 episode 12: "Agent Hartford" had no fingerprints: the FBI "removed" them. But when they find the street piece that Vinny had, they dust it and say that Hartford's prints were all over it. This might be OK, if he were a real agent on the books (but they never heard of him at Quantico), or if he were a real criminal - but in that case, they would have sussed it all out earlier.
Blood Moon - S11-E3
Continuity mistake: When Nick is talking to Catherine about what happened at the night of the murder he folds his arms. In the next show they are unfolded. Although you can't see his arms entirely, it becomes clear from the position of his shoulders and the wrinkle in the middle of his shirt that instantly disappears.
And Then There Were None - S2-E9
Factual error: Ballistics expert Bobby Dawson mispronounces the word "Koch" in the term "Heckler and Koch". He pronounces it "kotch" instead of the correct, "koch" (rhyming with lock0. A ballistics expert would know the correct way.
Plot hole: Episode 9-18, "Turn, Turn Turn": Greg states that the dead motel manager crawled up into the ceiling the same way that he did, and you see Nick open the access panel in the ceiling. The manager couldn't have closed the ceiling panel after him and no one was managing the hotel in the week he was missing. The panel should have been open when Nick came into the room. The new manager stated he didn't know if there was a panel in that room, since he just got there.
Hitting for the Cycle - S11-E18
Continuity mistake: Series 11, Episode 18, "Hitting for the Cycle": At the very beginning of the episode they are talking about the cycle while looking at the board. The three main ones, Suicide, Accidental and Homicide, are together on cards with a space above and then two more cards. The scene then goes out to show the CSIs again, and there are now four cards grouped together on the board.
Character mistake: Brass tells Dream (pleasure services girl) that whacking 'Happy Morales' with a tire iron - which contributed to his death - is open grounds for assault and murder-1 on her. When it was purely a self-defense act, that any of the girls would have taken against a psychotic, oversexualized maniac, in such sexual assault. Whether it be a tire iron, or other heavy-duty object to dispel a perp.