Rustin Spencer "Rust" Cohle is a fictional character portrayed by Matthew McConaughey in the first season of HBO's anthology television series True Detective.

He works as a homicide detective for the Louisiana State Police (LSP) alongside his partner Marty Hart, portrayed by Woody Harrelson.

[1] Cohle is introduced as a gifted but deeply troubled detective who has newly transferred to the LSP's criminal investigation division (CID).

[2] Cohle spends his free time obsessing over every detail of the crime, hoarding evidence and keeping extensive notes in a ledger, which earns him the derisive nickname "The Taxman" among his colleagues.

Devastated by the loss, Cohle grew evermore unstable, eventually killing a crystal meth addict who had injected his own child with the drug.

They discover that the killer raped and tortured the victim, a prostitute named Dora Lange, and subsequently attached a pair of deer antlers to her head, painted a spiraling vortex on her back, and posed her underneath a tree in a burnt sugarcane field.

The murder becomes a local media sensation, attracting the attention of reverend Billy Lee Tuttle, cousin of the state governor, who together seek to assemble a task force related to crimes deemed anti-Christian, much to Cohle's chagrin.

Seeking a rural brothel in Vermilion Parish called the Ranch, Cohle assaults some local johns and uncovers its location.

In the wreckage of a burnt-out church Lange attended, they find more structures and a painting on the wall depicting a human figure wearing antlers.

[3] Cohle and Hart work the case for three months, during which they trace the murder to Reggie Ledoux, a former Avoyelles prison cellmate of Lange's ex-husband, Charlie.

[5] They learn that Reggie manufactures crystal meth for an East Texas-based outlaw motorcycle club called the Iron Crusaders, whom Cohle has a history with from his time undercover.

Cohle steals cocaine from the evidence lockup and meets with the Iron Crusaders while posing as a drug dealer representing a group from Mexico.

Cohle becomes obsessed with reopening the case and pursues several leads, including a private Christian school run by Billy Lee Tuttle that had been closed amid rumors of child sexual abuse.

He also visits the Ledouxs' surviving victim, now institutionalized with catatonia, who tells Rust about a third attacker, and begins screaming when Cohle asks her about the man's apparently scarred face.

[8] In 2012, a murder similar to the Lange case from 1995 occurs and Cohle is seen in the vicinity of the body, arousing the suspicion of LSP detectives Gilbough and Papania.

[8] Cohle meets with Hart, who has also quit state CID and runs his own private investigation firm; he tells him that he has found evidence leading to the killer.

Cohle and Hart track down the original case's chief investigating officer, Sheriff Steve Geraci, and interrogate him at gunpoint.