While filming on location in downtown Los Angeles, an actual dead body was found in an apartment building, several floors down from the film crew's location. The body turned out to be the mummified remains of a long-dead tenant. The main cast was not on set at the time. In an ironic twist, one of the cases in episode 302, "Not What It Looks Like," involves a missing woman whose mummified body is found in an abandoned apartment.
While the majority of the techniques and technologies used in the CSI shows are accurate and true to reality, the writers and crew readily admit that they "time cheat". Tests that take seconds in the show often take days or even weeks in real life.
Danny Messer claims that he had a short-lived career in the music business, and that he quit baseball when he broke his wrist in a fight. Carmine Giovinazzo, the actor who plays Danny, admits that he quit baseball because of a back injury, and that he often brings his guitar to the set and plays for his co-stars.
Anthony E. Zuiker wanted The Who's "Behind Blue Eyes" ("Blue" being a figurative term for a police officer) to be the show's theme song. However, CBS president Leslie Moonves turned it down in favour of "Baba O'Riley" (also by The Who).
In real life, the New York City Police Department (NYPD) Crime Scene Investigators (CSI's) are not detectives and are called Forensic Technicians who work in teams called Crime Scene Units (CSU's). Most present day applicants are surprised to discover that the CSU's do not perform most of the tasks depicted on the series. E.g. They do not interview suspects, they do not write or execute search warrants, and they do not make arrests. In real life they are directed around the scenes by the detectives and supervisors, not the other way around. Detectives are commissioned police officers (sworn personnel). CSU's are civilian personnel, not sworn and do not have the same arrest powers as police officers. However they are very skilled technicians, and are a component of the police response to crime.
Sela Ward's character is named Josephine, but is referred to as Jo. In Sisters, her character was Theodora, referred to as Teddy. All of the sisters had names that had naturally male sounding nicknames because their father always wanted a boy.
The cell phones that are used are Palm Treo 650's. Beginning season 3 they use Nokia E62's. By the third show of season four, Detective Mac Taylor now has the newest Treo - a blue 755p, which is also available in burgundy.
When deciding where to set the next CSI, Anthony E. Zuiker had 3 cities at the top of his list Chicago, New Orleans and New York. He quickly chose New York after he remembered the effect 9/11 on the city. There are references to both Chicargo and New Orleans as Mac Taylor is from Chicago and Stella Bonasera leaves for the New Orleans CSI Lab.
At the conclusion of each case the culprits almost always confess their guilt to investigators that would most assuredly not be the people interviewing them, this helps to wrap up the case in a Scooby Doo like manner for the general viewing public.