It is alleged Alf Eades died after being assaulted by six men in his cell on February 26, 2019.
The five men on trial are Brandon Taylor, Clinton Penny, Cooper Clay, Liam McGlade and Shaun Kapene.
It is alleged they punched and kicked Mr Eades, who received massive head injuries.
The court has heard at least one of the men allegedly jumped on his head.
Mr Eades suffered severe head injuries and he passed away in hospital on March 11.
Prosecutor James Mactaggart told the court the victim was in his 40s, while his attackers were all young men.
He said a witness would give details of the assault to the court that he believed it happened on the orders of a bikie gang member, as he was told he would have to "answer to the Comancheros" if he did not participate.
The prosecutor said the "level of violence escalated" soon after the men entered Mr Eades's cell, saying the blows were "focused, concentrated and powerful".
Mr Mactaggart said the assault lasted several minutes and first responders faced a "truly horrific" scene, having to mop up blood using towels.
Attacker 'did not intend to kill', lawyer says
Michael Tudori, representing Mr Taylor, said he denied intending to kill Mr Eades.
He told the court that while his client "was in the cell", his intention was to commit an assault.
Mr Tudori said Mr Taylor "was there to touch him up and that was it".
He told the jury it was "very important you keep an open mind".
A second defence lawyer, Jonathan Davies, told the court the other prisoners were lying about the involvement of his client, Mr Penny.
"Ask yourselves, who is lying and why," he said.
Mr Davies also said there was "surprisingly" no CCTV footage available.
"Where were the prison officers?" he asked.
"We're not sure but we'll be asking questions about that".
Mr Davies asked the jury to focus on whether the forensics were reliable.
Simon Freitag, representing Mr McGlade, said the case against his client — that he "punched and kicked" Mr Eades — "principally" relied on one witness.
Mr Freitag told the court Mr McGlade had "nothing to fear from the DNA evidence" because the state would not be bringing any such evidence against his client.
Paul Bevilacqua, for Mr Clay, simply said an allegation had been made and his client denied it.
Graeme Allen, appearing for Mr Kapene, chose not to give an opening address.
The trial is set down for 30 days.