A potent small-screen presence

Since its 2000 premiere, "CSI: Crime Scene Investigation" has distinguished itself with cool science. While the murders in the casinos and on the streets of Las Vegas do involve sex and violence, two of crime TV's mainstays, "CSI" ultimately brings everything back to the lab for objective analysis. "CSI" would be nothing special -- and certainly not such a classic piece of DNA-era entertainment -- without its sterile tweezers, swabs, and microscopes.

The show would also lose something definitive without William Petersen as lead investigator Gil Grissom. Petersen embodies the quietly intense tone of inquiry at the core of the CBS drama. Nothing fascinates his Grissom quite so much as the scientific logic inherent in a crime scene -- not office politics, not love interests, not family. He is unlike most of TV's crime-solving detectives in his worship of reason . While his counterparts on spin offs "CSI: Miami" and "CSI: NY" are less tethered to the crime-scene evidence, as they get swept up in their own emotional issues, Grissom remains almost obsessively focused on it.

Petersen, who is on sabbatical from the show, may project out in his stage work, but on "CSI" he plays down. He wisely lets the camera find him, and he seems to land at the center of a scene rather than having made a play to be there. Grissom is low key, but he's not shy, and he comes to the fore because of his ideas, or his suspicions. He's an intellectual, filled with rarefied knowledge, but he doesn't flaunt his smarts; he only shows them when relevant, or for the sake of a sly joke. In his slightly geeky way, he can be quite the comic.

To some extent, Petersen has made Grissom into a counterpoint to Las Vegas. He's unnervingly sober in a town known for its compulsive behaviors. Throughout the show's seven seasons, he has rarely succumbed to temptation -- his affair with Sara (Jorja Fox) has been one of his few moments of intoxication. He clearly has some inner turmoil, with his broodish manner, and yet he never appears to be on the verge of exploding.

Petersen came to "CSI" as an actor who had done enough significant work, particularly in the Michael Mann film "Manhunter," to be recognizable but not easily identifiable. And his acceptance of that status has helped him keep Grissom modest. If Petersen had been on the prowl for major stardom, he probably would have had to compromise the character he has so vividly created. The last thing we want is to see Grissom losing his reserve and acting out, or Petersen angling for an Emmy.