"The CSI Effect": The investigation team routinely photograph 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).
In many episodes, a suspect is found because a gun was registered to them or someone is threatened with the charge of "possession of an unregistered firearm", or some other reference is made to a firearms registration database. The state of Florida has fairly relaxed gun control laws, and there is no gun registration system anywhere in the state.
"The CSI Effect": In many occasions, when arresting a suspect, Horatio's 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. Also, numerous times when Alexx is performing the autopsy, she has a mask tied around her neck but is not actually wearing it. This mask would always be worn during autopsy to protect the person performing it from breathing in airborne pathogens the body may put into the air. Her hair is also not tied up or covered, which could also cause cross contamination.
In the Czech dubbing of the series, the female character Maxine Valera is often referred to as a man, "Valera" being "his" first name. This is caused by the lack of knowledge of the translators in terms of first name/last name usage in the United States. In Czech, a name sounding similar to "Valera" would be men's name.
On numerous occasions, suspects are given a "perp walk" from the front door of the police building to a waiting squad car or jail bus. While this provides for good drama (reporters, angry relatives of dead victims, etc.), such prisoner transfers are supposed to take place away from public view, to avoid the public spectacle portrayed in the show.
"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."
"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.
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.
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 MDPD 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 crime scenes, 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.
"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.
"The CSI Effect": In many episodes the CSI team 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 the CSI series.