Twelve prisoners were yesterday charged over the death of a fellow inmate at the Kandal Provincial Prison, after his alleged killing was initially ruled a suicide.

Mut Linan, 31, was in pre-trial detention for two days in a cell with 73 others when he was allegedly attacked and killed last month. Officials initially told his grieving mother that Linan died after he jumped from a 1.2-metre height – a scenario that seemed at odds with the severity of his injuries.

A court official who asked not to be named yesterday said prisoner Moeun Hoeun, who had been assigned as a kind of “security guard” in the cell, allegedly “gave an order to the other prisoners to beat the victim” because Linan was shouting and Hoeun couldn’t sleep.

Three suspects named Seng Da, Leng Rith and Samal Uddom then allegedly assaulted the victim, beating him to the point of unconsciousness. Seven other prisoners allegedly took part in the violence, but it is believed they did not lay the final, fatal blows.

The official said another prisoner, Mok Nuon, was assigned to be the chief of the cell, an unofficial role that requires alerting prison guards stationed 10 metres away to any problems. Instead, Nuon allegedly sat back and watched.

According the official, Nuon also concocted the cover story that Linan had “fallen” from the top of a water tank. He also allegedly told the three key attackers to bring him $500 each and he would make the case go away.

Prosecutor Ek Sun Reaksmey yesterday said Hoeun was charged with instigating intentional violence resulting in the death of the victim, along with Da, Rith and Uddom. They face between seven and 15 additional years in prison if convicted. Nuon was charged as an accomplice to the same crime.

The seven other prisoners were charged as accomplices to intentional violence, and face between one and three years behind bars.

Nut Savna, spokesman for the General Department of Prisons, said the inmates must take “criminal responsibility for what they have done” and that “if the prison officials were involved, we will take action accordingly”.

“The prison must strengthen the internal rules and ensure prison officials . . . are careful when assigning security guards,” he said.

Kandal Provincial Prison Director Chat Sineang claimed he had already bolstered prison discipline by reminding prisoners, each Saturday, what to do when fights break out.

“If there is a quarrel, they have to shout and hit a bucket in order that we go in to intervene,” he said.

“I am the prison chief, how can I go to sleep in the cell with detainees? . . . We were not careless, but I accept that it is under my management.”

But rights advocates said the practice of assigning inmates to be unofficial security guards and chiefs over their peers was fraught, as they lacked accountability.

Chak Sopheap, from the Cambodian Center for Human Rights, said she welcomed responsibilities being given to prisoners to help them reintegrate into society, but protecting the safety of inmates was the sole duty of the state.

“Such duty . . . can never be delegated to non-state actors, including prisoners; doing otherwise could [pave] the way for abuses,” she said in an email.

The victim’s mother, Long Vanny, said her son’s death “should never have happened”, noting that he was in jail awaiting trial for the minor crime of property damage.

“I really regret his death . . . They should strengthen the regulations in the prison so something like this cannot happen again.”

Additional reporting by Erin Handley