Dr. Raymond Langston (Laurence Fishburne) is a Level 2 Crime Scene Investigator on the hit show "CSI." Dr. Langston had been a pathologist and a professor but was recruited to join the CSI crew by former CSI supervisor Gil Grissom (William Petersen) after assisting in a CSI investigation involving convicted serial killer Nate Haskell (Bill Irwin). After some assistance by current supervisor Catherine Willows (Marg Helgenberger) and co-workers Nick Stokes (George Eads) and Riley Adams (Lauren Lee Smith), Dr. Langston has become an integral part of the CSI team.
Dr. Langston is obsessed with serial killers. A co-worker at a hospital where he worked killed 27 patients. Although Dr. Langston had seen the clues, he had never been able to piece them together. Soon after becoming a CSI, a serial killer named Dr. Jekyll begins taunting him. Dr. Langston seeks the assistance of convicted serial killer Nate Haskell to solve the case but is stabbed by Haskell and left for dead.
His obsession with serial killers comes from his concerns about his own violent tendencies. His father was in the military and was often very violent with his son. Dr. Langston believes there is a gene that can predict whether a person will become a serial killer. He believes he and his father have this gene, which causes him to refuse to give a DNA sample to the CSI lab.
Willows: "What are the odds, right?"
Dr. Langston: "Before it happened I would've said slim. But since it did happen -- a hundred percent.
Willows: "Seems like a lot of things keep falling out of the sky, right? Poison, people, turtles."
Dr. Langston: "Tortoises."
Willows: "Whatever. Maybe I should start wearing a helmet."
Dr. Langston: "Or at least carrying an umbrella."