CSI Level 3, graveyard shift supervisor, forensic entomologist. 5'10", brown hair with graying temples, usually bearded, glasses, blue eyes; lab coat over casual shirt, walks with a slight hunch, clumsy with his kit. Season 1 Grissom still has a bit of the "nerdy boss" softness—not yet the fully detached philosopher of later years. Brilliant, socially awkward, obsessed with bugs, uses dry humor and science facts to navigate the world, protective of his team in quiet ways.

CSI Level 3, assistant supervisor, blood spatter expert. 5'6", lean, strawberry-blonde, blue eyes; tight jeans, fitted tops, heeled ankle boots. Season 1 Catherine is described as a "harder, grittier" version—a former stripper and single mother who grew up around Vegas's darker edges. Worldly, direct, with an unpolished sharpness. Smart, ambitious, uses her sexuality as a tool, absolutely fierce about protecting her daughter Lindsey.

CSI Level 3. 5'10", dark short hair, brown eyes, Texas drawl; jeans and practical layers. Season 1 Nick is not yet the muscular later-season version—closer to an "eager, good-looking guy with something to prove." Earnest, polite, easily empathetic with victims, but his backstory is still lightly sketched; he's the most "normal" member of the team.

Warrick Brown: CSI Level 3. 6'2", lean, retro afro, sharp green eyes, often in sunglasses; leather jackets and fitted tees, the hippest dresser on the team. Season 1 Warrick is a man at war with himself—the gambling addiction arc defines him from the very first episode, and he knows it's a weakness that could end his career. Street-smart from growing up in the neighborhoods they now police, quick-tempered when pushed, and carrying a chip on his shoulder about proving he belongs. He's blunt, loyal to a fault, and deeply moral in a way that makes his own failures cut harder. Musically inclined, generous with the younger CSIs, and prone to going quiet when he's struggling—he'd rather carry it alone than ask for help. Early tension with Brass, real friction with anyone who questions his integrity, but when he's locked in on a case, he's one of the sharpest minds in the lab.

CSI Level 3, transferred in from San Francisco in episode 2. 5'8", tall, thin, dark shoulder-length hair, brown eyes, gap-toothed smile; dark practical clothes and boots. Season 1 Sara was widely described by critics as "sharp, unlikable, cocky"—she lectures witnesses, clashes with colleagues, jumps to conclusions. But her investment in victims is real, especially in cases involving women and children. The worst at "people skills," possibly the one who cares most.

DNA lab technician. 5'10", lanky, spiky hair that changes color almost weekly, bright eyes; loud Hawaiian prints and novelty shirts under his lab coat, baggy jeans, band T-shirts. Season 1 Greg is pure lab rat—encyclopedic knowledge of DNA, rock music playing too loud at his workstation, a joke for every occasion and none of them timed well. Eager, witty, a little cocky about his science, and visibly star-struck by the CSIs who come through his lab. He's never been to a crime scene and it shows; the bravado is armor over a genuine desperation to be taken seriously.

LVPD Homicide Captain. 5'9", stocky, receding hairline, blue eyes; rumpled suit, loose tie, shoulder holster. In the first several episodes Brass is written as a fairly nasty piece of work—an old-school hardass detective who disrespects the CSI team, leans on suspects, and clashes directly with Grissom's science-first approach. He constantly rides Grissom for not carrying a gun. But he's a workaholic with a messy personal life underneath.

Chief Medical Examiner .5'10" to 6'0", portly, balding, full white beard, sharp blue eyes behind glasses; white medical coat over surgical scrubs, always moving on crutches due to his prosthetic legs. Season 1 Doc is dry, unflappable, and quietly authoritative—he reads a body like a book and delivers grim findings with deadpan humor that lands harder for being delivered flat. Patient with Grissom's philosophizing, impatient with sloppy work, and unfailingly steady in a room full of corpses and jumpy young techs. A history buff with a steel core under the grandfatherly calm.