A doctor charged in connection with the death of Friends star Matthew Perry has pleaded guilty to a charge of conspiring to distribute the drug ketamine.
Dr Mark Chavez appeared in a Los Angeles court on Wednesday to enter his plea.
The 54-year-old could face up to 10 years in prison.
A medical examiner later ruled that ketamine was the primary cause of death.
The 54-year-old actor had been taking the drug six to eight times a day before he died, according to court documents.
Chavez’s lawyer Matthew Binninger said after his first court appearance in August that he is “incredibly remorseful” and is “trying to do everything in his power to right the wrong that happened here”.
The other four are Iwamasa, an acquaintance of the actor named Eric Fleming, another doctor named Salvador Plasencia, known as “Dr P”, and Jasveen Sangha, who was referred to in documents as the “Ketamine Queen“.
Chavez is the third person to have pleaded guilty in the case.
Iwamasa has pleaded guilty to one count of conspiracy to distribute ketamine causing death.
He’s also admitted repeatedly injecting Perry with ketamine without medical training, including on the day he died.
Meanwhile, Fleming, 54, has pleaded guilty to one count of conspiracy to distribute ketamine and one count of distribution of ketamine resulting in death.
He admitted to giving Iwamasa the ketamine that killed Perry.
Chavez, Fleming and Iwamasa were offered lesser charges in exchange for their cooperation as prosecutors go after their main targets in the case – Plasencia and Sangha.
Plasencia has been charged with illegally selling ketamine to Perry in the month before his death while Sangha is alleged to be a dealer who sold the actor the lethal dose. Both have pleaded not guilty and are awaiting trial.
Chavez admitted in his plea agreement that he obtained ketamine from his former clinic and from a wholesale distributor where he submitted a fraudulent prescription.
Although he faces up to a decade in prison when he is sentenced on 2 April next yeat, he is likely to be sentenced to far less because of the plea and his cooperation with prosecutors.
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Perry had been using ketamine through his regular doctor in a legal but off-label treatment for depression that has become increasingly common.
He eventually began seeking more ketamine than his doctor would give him.
About a month before his death, he found Plasencia, who in turn allegedly asked Chavez to obtain the drug for him.
“I wonder how much this moron will pay,” Plasencia texted Chavez, according to court filings from prosecutors.
The two met up the same day in Costa Mesa, halfway between Los Angeles and San Diego, and exchanged at least four vials of ketamine, the filings said.
After selling the drugs to Perry for $4,500 (£3,391), Plasencia allegedly asked Chavez if he could keep supplying them so they could become Perry’s “go-to”, prosecutors said.
US Attorney Martin Estrada said in announcing the charges on 15 August that “the doctors preyed on Perry’s history of addiction in the final months of his life last year to provide him with ketamine in amounts they knew were dangerous”.
Perry struggled with addiction for years, dating back to his time on “Friends,” when he became one of the biggest stars of his generation as Chandler Bing.
He starred alongside Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer for 10 seasons from 1994 to 2004.