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.
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.
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.
Although the CSIs are also detectives, this is exceedingly rare in actual life. 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.
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.
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.
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.
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.