Now, three of them are accused of allegedly beating up and sexually assaulting the other inmate.
Iryan Abdul Karim, 21, Muhammad Hamdan Abdul Rahman, 20, and Mohammed Zameen Abdul Manoff, 21, are said to have committed the offences at the Changi Prison Complex between Apr 27 and May 4 last year.
There is a court order against naming the victim, who has since finished serving his sentence.
During that time, the trio allegedly attacked the victim by punching, jumping on and stepping on his chest and kicking his body several times.
On Apr 29 last year, they allegedly forced the victim to swallow human faeces.
As a result of the brutal attacks, the victim suffered a fractured jaw and lower breastbone, six fractured right ribs, four fractured left ribs, and several fractured vertebrae.
Yesterday, the joint trial of the trio was supposed to start before Justice Tay Yong Kwang at the High Court.
The three, who are still in prison, did not have lawyers.
After the charges were read to them, Iryan and Muhammad Hamdan said that they wanted to plead guilty to the ones that were related to the physical assault and making the victim eat faeces.
They are claiming trial for the alleged sexual offences.
Iryan, Muhammad Hamdan and Mohammed Zameen allegedly forced the victim to perform oral sex on each of them in April and May.
Plead guilty
Mohammed Zameen also wanted to plead guilty to beating up the victim. But he denied sodomising the victim and forcing him to eat faeces.
Arrangements will be made for them to plead guilty before another High Court judge.
Justice Tay adjourned the trial on the disputed charges to next week.
The three men asked that their names not be published in media reports, but Justice Tay turned down their request.
PENALTIES:
For voluntarily causing grievous hurt, they can be jailed 10 years and caned.
For voluntarily causing hurt, they can be jailed a maximum of two years and fined $5,000.
For sodomy and forcing the victim to perform oral sex, they can be jailed 20 years and caned.
For forcing the victim to eat human faeces, they can be jailed seven years and caned.
