So cutting-edge he sometimes injures himself, Greg Sanders joined the Las Vegas CSI lab as a DNA technician on the graveyard shift. We first meet Greg drumming along with his stereo while waiting for assay results, and his passionate love of music, 80's-inspired hair and t-shirts, and irreverence to authority become running themes thereafter.
A full-scholarship Stanford Chemistry grad and erstwhile high school Chess Club captain, Greg is an only child. He describes his parents, especially his mother, as being completely devoted to him, and rather than rebelling against them, Greg turned his natural quirkiness inwards. He professes a love of goth-rock and glam-pop rock, recreational latex club wear and body-painting, surfer girls, SCUBA diving, top-quality gourmet coffee and various but unconfirmed sexual kinks. In later seasons, he also becomes fascinated with the white-collar mobsters and history of Old Vegas, about which he writes a book.
Greg has Norwegian roots, as evidenced by his mother's maiden name, "Hojem", his anecdotes about his grandfather, Papa Olaf, and - to his chagrin - his susceptibility to a strain of foot fungus that affects people of Scandinavian heritage.
After a day of field work, during which all available hands are called to assist with a catastrophic bus accident, Greg confesses that he feels constricted by lab work. The team is quick to support his move into the field, especially Grissom, who is impressed with Greg's attitude of "not being about the money." CSI Sara Sidle, for whom Greg harbours an unsubtle torch, is assigned as his key mentor through his training as a field CSI. Sara responds to his overtures with amused tolerance, and over the years, their friendship settles into a strong bond that they come to rely upon. Within the year, Greg passes all his proficiency exams, and becomes a CSI Level 1, welcomed with champagne by the team. His fellow lab rats are largely supportive, with the notable exception of David Hodges, who takes any opportunity to complain.
As the little brother of the team, Greg visibly matures through the series, sometimes painfully. His hyperactive, bored-genius antics are regarded with eye-rolling amusement by the others, but when Greg is injured in an accidental lab explosion, they quickly rally round him, and he realizes that they consider him part of the team. Later, during one of his first solo callouts, Greg is attacked by a wandering mob of youths, and is beaten nearly into a coma. The subsequent criminal and civil trials, in which Greg is accused of murdering or causing the death of one of the attackers, leaves him a sadder and wiser man. There is no grand emotional realization to be gained in such cases, and he simply has to learn to absorb such events as part of a law enforcement officer's career.
On his way to LA to meet with publishers about his Old Vegas book, Greg is called back to the lab by Catherine, with the news that Warrick has been killed. Greg is visibly shaken, but deals with his shock and grief by staying busy, helping Sara make Warrick's funeral arrangements. It is he who first discovers that Warrick has a son.
Greg, having served as a sort of "everyman-audience" figure as he progresses, rises to his own challenge: earning a track record as a reliable CSI, and coming to terms with the emotional and practical realities of the job. Recent episodes show him as a settled career CSI Three, focussed on his job and at least looking the part of a respectable criminalist and expert witness - though still very much Greg.