The courts have heard that the two Mongrel Mob members were motivated by taking Lui's Outlaws patch as a trophy. The Crown described it as "quite literally … a target on his back".
Te Aonui-Tawhai pleaded guilty to murder, assault and the aggravated robbery of Lui's Outlaws patch. He was sentenced last month to life imprisonment with a minimum non-parole period of 13 years.
Cahill pleaded guilty to aggravated robbery but elected for trial by jury for assault with a weapon and murder.
In July, a jury found Cahill guilty of the assault, but could not agree on a verdict for the murder charge.
A second trial had been scheduled for February next year, but Cahill pleaded guilty to murder in the High Court on Thursday after receiving a sentencing indication.
Justice Helen McQueen convicted Cahill and remanded him until November 18 for sentence. He was already in custody.
Through his lawyer, Eric Forster, Cahill offered to apologise to Lui's family through a formal restorative justice programme.