A killer beheaded another murderer and cut off several of his body parts in a gruesome attack at a prison, a court heard.
Jaime Osuna is alleged to have used a makeshift weapon, described as a sharp object wrapped in string, to repeatedly cut cell mate Luis Romero in a sadistic attack last month.
The killing happened overnight on March 9 at Corcoran state prison near Sacramento, in the US, with the body of 44-year-old Romero discovered by guards the following morning.
He had bled to death from multiple wounds and his body had been mutilated, a post-mortem revealed.
An eye, finger and part of one of Romero's lungs had been removed.
Prosecutors say it is likely Romero was alive for part of the attack and Osuna, who is serving life without parole for the brutal 2011 slaying of Yvette Pena, could face the death penalty as the incident was "especially heinous, atrocious, or cruel, manifesting exceptional depravity".
The 31-year-old has been charged with murder, torture, mayhem and weapons possession.
The torture charge alleges he acted "with the intent to cause cruel and extreme pain and suffering for the purpose of revenge, extortion, persuasion and for a sadistic purpose".
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He denied the charges during a court appearance this week.
District attorney Phil Esbenshade described it as the "most gruesome case" he had ever seen "in terms of heinousness in the slaying".
The California Department of Corrections and Rehabilitation are investigating how the incident happened.
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Osuna has now been transferred to a mental health and medical care prison, but officials have not revealed the reason for the move, citing privacy laws.
In 2017 he was jailed after admitting killing 37-year-old mum-of-six Miss Pena.
Her gagged body was found at a motel. Knives were protruding from her back.
He only escaped the death sentence then after striking a plea deal with prosecutors.
Romero was also serving a life term with the possibility of parole imposed in 1992 for a Los Angeles killing.
