It's pretty obvious that the fictional CSI type shows are just that; fictions. So unless you actually become an actor on those shows, you won't really be doing that sort of work IRL.

If you want to know what real detectives and CSI's do, I suspect you'll want to check out some of the shows on A&E, CrimeTV, Discovery, etc... I don't know how really factual they are, but shows like "First 48" and similar are a better view of what really happens then the Crime of the Week Drama's on the main networks.