Purportrated to be as realistic as possible, using actual procedures in the field and actual equipment in the lab. And I heard that they often base their stories on real events.
But the problem with the show as a "Who done it" is that the writers are always trying to shock their viewers as to who the killer actually is.
Knowing this going in produces the opposite effect and makes the show as predictable as Scooby Doo. For example, one of their favorite things to do is having children: teenagers, pre-teens, and sometimes even toddlers be the killer.
Some cast members:
Gil Grissom: The head of the team and a bug expert. Likes roller coasters.
Catherine Willows: Second in command and ex-stripper. Has a mob boss as a Father.
Warrick Brown: An ex-gambling addict who always looks like he's in pain.
Nick Stokes: Used to have a penchant for the ladies, but they kind of low-keyed that when the actor started losing his looks.
Sara Sidle: Advocate for abused women. I think the main reason she's there is because her name sounds like "suicidal".
GF: CSI. I think the Father killed his wife.
ME: Father? They have a kid?
GF: Yeah, an adorable 10 year old girl.
ME: Oh... well it wasn't the Father. It was the little girl.
(2nd person) No, dude. So whats all those strands for anyway?
(1st person)So that's why you got caught!