Gilbert 'Gil' Grissom, played by William L. Petersen, is the nightshift supervisor of the Las Vegas CSI (Crime Scene Investigation) lab. He is the character with the most quirks on the show, a nice touch that gives his over ethical and calculating tendencies a human element. Though Grissom attempts to be aloof, he is very attached to the people in his unit.
Gil Grissom, known often as simply Grissom, is not only a forensic scientist, he is also a well known entomologist, a talent that he uses in many of his cases. He is the quirkiest character on the show with many strange habits that confuse the other CSI's. He also isolates himself from human contact, causing issues with his unit and local politics. Whenever Grissom encounters an emotional problem, he rides roller coasters.
Emotional problems were a large portion of Grissom's life with the introduction of Sara Sidle, a CSI that Grissom brought from another unit . Sara is an outspoken woman and at one point was a potential love interest of Grissom. This tension between the two is truly discussed in Butterflied when the CSI team has to investigate the murder of a girl who looks strikingly like Sara.
Grissom is dealing with the genetic disorder otosclerosis, the same disease that made his mother deaf. He refuses to tell the rest of the CSI team that he is losing his hearing. It is also hinted that Grissom has Asperger's Syndrome (a form of autism) in Caged.
- Pilot — Grissom is sent to investigate an apparent suicide in a bathtub.
- After closing the case of the Dick & Jane Killer, he gave Raymond Langston his position and resigned from CSI. Then in Costa Rica, he reunited with Sara Sidle and shared a long kiss.
- Grissom puts red ants on his eggs.
- He races cockroaches.
- He is an avid fan of baseball.
- He was a Roman Catholic, but he now believes in God but not religion.
- He is one of around 15 forensic entomologist in the country.
- His father, a botany teacher, died when Grissom was nine years old.