"Think of his reality, his life is prison. That's his home so he has now identified himself as a nark. He has made his life far less positive when he made this decision. So why did he do that if what he had to say wasn't the truth?"
The Crown said the witness had been called into Leota's cell to find Poi lying unconscious in a pool of blood and told "Get your ******* mate out of my cell."
It was alleged Leota had beat Poi after hearing the plan to smuggle contraband into the prison had failed.
The court heard Poi suffered a serious brain injury and was no longer able to walk, talk or do anything for himself.
Manning said "it took guts" for the witness to come forward and urged the jury to put aside their prejudice when deliberating their verdict.
"You don't have to like him but you have to admire his fortitude. It took courage and it took character, not words you would normally associate with someone who is in prison for murder."
Defence counsel Bill Calver proposed the witness had "woven a tissue of lies" right from the beginning.
He said Leota had not anticipated the assault and that his efforts to clean his cell afterwards did not necessarily mean he was responsible.
"If Mr Leota had become aware someone had been assaulted you might very think that he would want his cell cleaned up so that he wouldn't get the blame for it."
Judge Clark is set to begin delivering her summary tomorrow morning.