"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.
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": 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": 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.
Throughout the series, probably to avoid copyright infringement issues, incorrect references are made to the New York Subway system. On subway entrances, the 1, 2, and 3 lines are shown in yellow, when they are actually red. A character blames his lateness on the fact that the Q train was changed to an express, whereas in real life the Q is normally an express.
"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 that are simply not possible in the real world.
"The CSI Effect": In many episodes, the CSIs are shown taking photos from crime scenes, then enlarging and enhancing them to get clues that let them solve that week's 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.
"The CSI Effect": Crime scene investigators and crime lab technicians are two separate groups. CSIs are involved in examining and collecting evidence at crime scenes, while crime lab technicians examine the evidence in the lab.
"The CSI Effect": The series does not show the less glamorous side of forensic science, as real-life CSIs 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": CSIs 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.
"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 CSIs constantly ask the detectives working with them to put out APBs (All Points Bulletins) or BOLOs (Be On the Look Out) to bring suspects and witnesses in. When found NYPD just walk up to people and place them in the squad car, taking them to the station for the CSIs 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.
"The CSI Effect": On many occasions, when arresting a suspect, Taylor's team is able to extract a confession, but the Miranda rights are never read to the suspect, which can and will be used to render the confession unusable in a court of law.
CSIs (Crime Scene Investigators) are actually called CSUs (Crime Scene Units) in the City of New York. However, this is most likely a deliberate change to better tie in the series as existing in the same universe as CSI: Crime Scene Investigation and CSI: Miami.
When the CSIs 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. However, with the invention and advancements of GPS and smartphones, it's not entirely unsurprising that locating suspects is shown to be achieved with relative ease.