What forensic specialty is Gil Grissom known for on CSI?

Gil Grissom is known for forensic entomology on CSI: Crime Scene Investigation. This specialty applies the study of insects and other arthropods to legal investigations, especially estimating the time since death from insect activity on a body.

Grissom, played by William Petersen, leads the Las Vegas crime-scene team during much of the original series. His scientific background is central to his character: he is portrayed as a forensic entomologist, biologist, and career criminalist with an unusually deep interest in insects and decomposition.

The answer is often confused with blood-spatter analysis, ballistics, or toxicology because all four are recurring forensic disciplines on CSI. However, blood-spatter analysis is particularly associated with Catherine Willows, while ballistics examines firearms and ammunition and toxicology studies drugs and poisons. Grissom may use evidence from all these fields, but entomology is his defining specialty.

The character helped popularize forensic entomology with television audiences, although the speed and certainty of CSI investigations are frequently more dramatic than real laboratory work.