Character mistake: Seven minutes into the show, Sarah Sidle is about to do an internal sexual assault exam/kit on an unconscious victim in the hospital, Sarah picks up a metal speculum and says aloud to the victim (in a presumed moment of empathy), that she "never really liked this part of my yearly exam. These things are always freezing" referring to the speculum in her hands. She then brings a speculum to her mouth and begins to blow open-mouthed on it two times, forcing her hot breath on it to warm it. She then begins to insert it into the victim as the scene cuts away. This is pure stupidity, as no trained CSI would ever contaminate the tool like this. Sarah just added her own DNA to the speculum via her breath so any saliva or body fluids are now on the speculum what she is about to use on this patient, who is now also exposed to any STDs from Sarah.
Factual error: Grissom and Catherine are looking through a microscope and discussing a microscopic specimen (heart of frozen body). In reality they would not see anything as all microscope objectives are missing on this instrument (the microscope nose-piece is totally empty.). (00:21:00)
Cool Change - S1-E2
Factual error: There are some majors problems with the "jumper's" crime scene. The girlfriend bashes the boyfriend on the back of his head. He bleeds out all over the balcony (she cleans up the blood with towels) but the body leaves absolutely no blood behind on the carpet (It's white\off white so blood would stain badly). She drags his body across the carpet and carpet fibers get stuck in his watchband by the adjustment knob. Dragging a body across the carpet would snag fibers on the opposite side. The CSI crew experiment and conclude the boyfriend was pushed. The blow to the head killed him instantly (coroner's report): therefore, the girlfriend would have dumped the body. Dumping a dead body over a rail would provide a different trajectory than pushing a live person and would not have matched their experiments. Finally, the boyfriend is fairly muscular and heavy. The girlfriend is petite. It would be an extremely difficult task to stand a lifeless body up at the balcony rail and flip him over. (If she could have lifted him up and over the rail, she should have been able to carry him to the balcony instead of dragging him.)
Cool Change - S1-E2
Plot hole: Grissom examines the victim's body and immediately rules it a homicide because he was wearing eyeglasses. He states that suicide is a cowardly act and no coward wants to see their death and would have removed their glasses before committing suicide. What a completely unfounded, and unscientific, statement. Suicide being an act of cowardice is his opinion and not a scientific fact and they don't work off opinions: they always state how they work off the evidence.
Suggested correction: This is correct, that was not scientific on Grissom's part, however this wouldn't be the last time Grissom formed an unscientific opinion that he was sure of based off what he thinks to he true as have the rest of the CSIs in several cases throughout the series. This also happens in real life; people involved in crime scenes making assumptions thus making errors off it. It wasn't right; but I would hardly call this a plot hole as this is something Grissom legitimately believes.
Audio problem: When Gil is talking to the drug dealer in the desert, he refers to him as a 'dumb punk'. But this has been dubbed over as what he actually called the dealer was a 'dumb prick' which you can tell by Gil's lip movements. (00:23:50)
Continuity mistake: While Sara is looking through missing person's files, Grissom comes in and starts talking to her. One shot her hair is in front of her face, the next it's behind her ear. This continues throughout the scene. (00:22:05)
Blood Drops - S1-E7
Factual error: The show falls into the Hollywood myth on polygraphs. Jesse is given a polygraph test after pleading guilty to the 4 murders. He answers all questions, except the last one, honestly. The 4 traces on the polygraph show no real movement on these questions. On the final question, Jesse lies and all 4 traces spike. If polygraphs actually did that, they would be admissible in court. But the reality is, it is the opinion of a highly trained operator that decides if there is a lie. The average person could not look at a polygraph results and point out a lie. There is no huge, visible spike. The producers could have replaced the 4 traces with a red\green light: Green is an honest answer and red a lie.
Continuity mistake: When Holly is first in Grissom's office and says that she feels light headed, Grissom offers her a chocolate-covered grasshopper and takes one for himself. Holly asks, "Is there a grasshopper in there?" and Grissom's right hand is near his waist. When the shot changes, Grissom merely smiles and eats the grasshopper, but his hand started off much closer to his chin without there being an opportunity for him to move it.
Continuity mistake: When Sara and Warrick are interviewing Meg at the end of the episode, the scene cuts between a medium shot of the dynamic duo, a close up of Meg's face and a close up of her hands which remain clasped on the table. The first time we cut to Meg there are tears in her eyes, but her face is dry. The second time we cut to Meg, there is a drying tear track on her right cheek. The third time we cut back to her, the tear track is gone, but there is a tear halfway down her left cheek. This continues throughout the scene.
Blood Drops - S1-E7
Continuity mistake: At the end, when Tina is shown the photos of Brenda they are in a pile of three. The camera cuts to a long shot and there are two in a row. Cut back to Tina and they are a pile of three again. This happens on and off throughout the scene.
$35K O.B.O. - S1-E18
Continuity mistake: In one shot Grissom puts a shoe on its side with a pencil. In the next shot the shoe is upright again.
Continuity mistake: When Catherine and Warrick are testing to find the distance the shots were fired from, when Catherine shoots at the shirt that's 2 feet away there is no gunpowder around the hole. When Warrick puts the victim's shirt next to it, for comparison, there is now an inch of gunpowder around the hole.
Revealing mistake: While the morgue's examiner opens Johnson's right eye with his fingers, the "corpse's" eyelid twitches repeatedly. (00:12:30)
Deliberate mistake: When the runner is shot in the back of the head in the SUV, the bullet has come out the front of his head. However, blood is seen on the windshield instead of a bullet hole where the bullet would have continued to go through the glass.
Revealing mistake: At the end of the episode, Grissom pins the newspaper article about the security guard's death onto the bulletin board and the camera zooms in on it. The article is three paragraphs long, however it is the same paragraph of text repeated three times. (A DVD player with a zoom feature can confirm this.) (00:44:30)
Who Are You? - S1-E6
Deliberate mistake: A plumber is looking for a leak under the floor of a house, and sees the bones of a hand sticking out of the concrete wall at the side of the house. The concrete is flat, this is because in construction boards are put up and the concrete is poured in, so how were the fingers sticking out of the boards during construction? In reality, the fingers would be inside the concrete, the workman would see nothing, no plot for CSI.
Blood Drops - S1-E7
Continuity mistake: Sara takes pictures of Brenda with an UV light camera. The camera used to film the episode for broadcast is barely able to show the walls in the background as tiled. When the UV pictures of Brenda are used in the interrogation, the photos show Brenda's back up against the tile wall.
Continuity mistake: When Gil and Catherine catch the couple in the bedroom, they are all sitting in the living room. Amanda is drinking a soda and it is about half full. Gil then asks for the straw. When we look at the soda again, it's full.
Continuity mistake: In the scene where Warrick pulls the piece of clothing from the toilet, the amount of water and dirt in the bowl changes between each shot. (00:14:00)
Cool Change - S1-E2
Revealing mistake: The male corpse's eye is fluttering as his arm is examined. (00:10:30)