In maximum-security prison, sometimes it's attack or be attacked.

That's what an inmate's lawyer told the Blake John Lee murder trial today in her closing address.

Paul Simon Tuliloa, Riki Wiremu Ngamoki and Lopeti Telefoni have all pleaded not guilty to murder.

Lopeti Telefoni says he didn't intend for Blake John Lee to die. Photo / Michael Craig

A fourth inmate stomped on Lee, stabbed him with a shank, then licked the lethal weapon at Auckland Prison in Paremoremo on March 5 last year.

Today, Telefoni's lawyer Emma Priest said Lee flashed a Mongrel Mob signal in the prison yard, and that gesture provoked a violent reaction.

Telefoni was a 20-year-old Crips member who'd only been in the jail for two days, Priest said.

He has admitted throwing the first punch, which floored Lee.

Priest said the gang gesture had made Telefoni paranoid, so he acted to neutralise a possible threat, and be a perpetrator instead of a victim.

Priest said this was a sad, depressing choice, but the reality of life in maximum-security jail.

Jurors heard the shank-wielding inmate, who has name suppression, was also with the Crips.

But Tuliloa and Ngamoki were members of the Killer Beez, she said.

Priest told jurors it was inconceivable her client would collude with the Killer Beez to attack Lee and Lee's friend, another Mongrel Mob inmate.

The Crown has argued the three men on trial engaged in violence to isolate Lee, render him helpless, and prevent Lee's friend from intervening.

The fourth inmate secreted a shank in his beanie before entering the exercise yard.

Priest said Corrections failed the inmates that day.

"His beanie was not checked. It wasn't scanned. It wasn't subject to a pat-down search."

She told jurors having eight inmates in the yard simultaneously was a bad idea.

Priest said Corrections had a 3-to-1 policy for safe entry, so 24 guards had to enter the yard if disorder erupted.

There weren't enough staff to do that quickly, she said.

Priest said Telefoni was obviously guilty of hurting Lee, but jurors must decide if he helped murder Lee.

And she said the Crown could not prove Telefoni had murderous intent.

Priest said the inmate with name suppression was not colluding with any of the three men on trial.

Security camera footage showed him licking the shank and taunting Lee's friend, she said.

"He's proud of his own individual actions."

Prosecutor David Wiseman previously said Telefoni stomped on Lee with his left foot and the fourth inmate stomped on Lee with his right foot.

But Priest said it was not accepted Telefoni stomped on Lee's head, and her client never saw the 15cm-long shank before the violence erupted.

The three prisoners on trial have admitted injuring with intent.

The trial before Justice Simon Moore and the jury continues.