"The CSI Effect": The investigation team routinely photographs the crime scene before allowing evidence to be touched or moved. Many times, however, a piece of evidence is picked up and handled before being photographed.
"The CSI Effect": CSI's and detectives sometimes pick up a weapon with a handkerchief or by inserting a pencil in the barrel. In real life, the handkerchief might contaminate possible DNA evidence, and the pencil would destroy microscopic markings inside the barrel, making it difficult to match the weapon to slugs retrieved from a victim's body or a crime scene. Instead experts recommend holding a weapon in place with gloved fingertips and sliding a thin, stiff sheet of plastic beneath it.
In the episodes where the blood is spattered or in a large pool, the pattern of the blood varies from scene to scene. For example: A man is killed and the blood is sprayed across a desk. The pattern in scene 1 (finding the body) will be different than in scene 2 (going back to the crime scene for further evidence).
"The CSI Effect": In many occasions, when arresting a suspect, the team is able to exact a confession but never the Miranda's right are read to the suspect, which can and will be used to render the confession unusable in a court of law.
"The CSI Effect": CSIs are not detectives as this is exceedingly rare in real life, as they are actually classed as civilian employees. It is considered an inappropriate and improbable practice to allow CSI personnel to be involved in detective work as it would compromise the impartiality of scientific evidence and would be impracticably time-consuming.
"The CSI Effect": While often the science and technology portrayed in the series (as well as the other CSI series) is accurate or mirrors sound scientific principle, there have been times when methods have led to results simply not possible in the real world.
"The CSI Effect": Numerous times, autopsies are conducted by people who were wearing the same clothes they wore in the field. Not only does this promote cross-contamination, but it is also highly unsanitary as well as an OSHA violation.
"The CSI Effect": The series does not show the less glamours side of forensic science as real life CSI's get messy with blood,fingerprints, etc. As one real world forensic scientist quoted, "After several hours on the scene it looks like I have taken a bath in fingerprint powder."
When the CSI's and detectives want to "bring in" or "pick up" someone for questioning, they are usually located instantly. That might work if they had a consistent schedule they followed faithfully every day, but there are few people who do that. Even with the invention and advancements of GPS and smartphones making it easier to locate suspects it should not be as simple as is portrayed in the series.
"The CSI Effect": Crime Scene Investigators and Crime Lab technicians are two separate groups. CSI's are involved in examining and collecting evidence at Crime Scenes whilst Crime Lab technicians examine the evidence in the lab.
"The CSI Effect": After lifting a fingerprint from a crime scene, and scanning it into a computer the results invariably comes up with a conclusive match to a suspect, This isn't the case in real life as much of the comparisons are done by comparing fingerprints by sight.
We see the CSI's constantly ask the detectives working with them to put out APB's (All Points Bulletins) or BOLOs (Be On the Look Out) to bring suspects and witnesses in. When found LVPD just walk up to people and place them in the squad car, taking them to the station for the CSI's to interview even though it's pretty clear they didn't want to come. If there is no probable cause for an arrest or an active arrest warrant, the police can't make you go anywhere against your will. Once in a while, a wealthy or educated person will assert this and ask a lawyer to be present but this is rare.
When the CSI's and detectives are interviewing someone or working a crime scene, they are never seen taking notes or sketching the crime scene. Real CSI's and detectives are constantly taking notes and sketching. The notes and sketches are so important that they are occasionally booked into evidence to ensure the originals will be available for review before trial.
In the opening credits of Season 1, there is a quick glimpse of someone (probably Warrick Brown) playing blackjack. Three sets of cards are visible - the one in the player's hand, scratching the table (calling for a hit) and two hands immediately to that player's left. Because blackjack is played from the dealer's left to right, the two hands to the player's left have not yet been played, yet the cards are face-down between their respective bets and the dealer. In a real game, the cards would have been dealt on the far side of the chips (toward the player). If the hands were in play, the cards would either be in the player's hand or under the chips (indicating a stand). As it is, the cards would never be in the position they are in. (Even if Warrick were playing all three of the hands, they would be dealt in alternating location - one in front of the chips and the next behind, never two consecutive hands in front of the chips.) Also, one of the hands is laid on the table such that it is partially covering its bet - something the casino would not allow because of the constant surveillance of the players' bets.
In a number of episodes people are shown eating and drinking in the laboratories. For instance, in CSI: Crime Scene Investigation: Ms. Willows Regrets Nick and Greg are seen eating fried chicken in the lab, and in CSI: Crime Scene Investigation: Overload Sara eats a sandwich while watching Grissom experiment with her deli pickle. There are other examples. No reputable laboratory (which this is supposed to be) would allow its staff to eat or drink while in the lab. It is basic scientific protocol to prevent contamination of samples or the person picking up toxins on their food.
Every time the investigators deal with IP-addresses, the addresses on display are impossible. Each of the four parts of an IP-address has to be between 0 and 255. As they do have to use IP-addresses some time, they could use addresses starting with 10. Those would be real addresses although not used as an official IP-address. This isn't the same as phone numbers using 555 - any IP address over 255 just wouldn't work. It would be like mentioning a phone number which uses the symbol for pi.
"The CSI Effect": In many episodes the CSI's are shown taking photos from crime scenes, then enlarging and enhancing them to get clues that let them solve that weeks crime. But in many instances, the original photo is blurry and out of focus and no matter how much you enlarge and enhance it you would not get the clear image of the clue that they always get on CSI.