Toxicology
From Memory Alpha, the free Star Trek reference
Toxicology is the scientific study of poisons and similar chemical substances on biological systems, specifically, the detection and treatment of conditions, as well as understanding the mechanisms and effects produced by these substances.
Doctor Beverly Crusher ran toxicological tests on the thirty-four crewmembers from the USS Brattain that were killed by each others hand to determine if the cause of their behavior was as a result of a virus, drugs, or a poison. Her tests concluded that there was no unusual substances in their systems. (TNG: "Night Terrors")
