In a first directions hearing on Tuesday, Justice Michael Brett ordered that two separate appeals on behalf of William Adair Rothwell, 18, and Jacob Michael Brennan, 17, be joined for the Court of Criminal Appeal.

The two youths pleaded guilty and are appealing the length of their sentences.

Justice Robert Pearce handed down the 26-year sentences in February after taking the extraordinary step of allowing the youthful killers to be identified in the interests of justice and to highlight heinous nature of the crime.

He said the men carried out the murder at Mowbray in August last year for a "trivial and dishonourable reason" and received a small amount of cannabis each as payment.

Counsel for Brennan Rochelle Mainwaring requested transcript and Justice Pearce's sentencing comments.

Justice Brett adjourned further hearing to a date to be fixed.

In sentencing, Justice Pearce ordered a non-parole period of 15 years, warned the Parole Board that it needed to think carefully about granting parole, particularly to Brennan, who stabbed Waters 18 times.

"Given the uncontrolled and unrestrained nature of the attack there could be future risk to the community upon release," he said.

"Before Brennan is released the Parole Board needs to carry out some psychiatric assessment on the level of danger that he poses."

Rothwell encouraged Brennan to be involved and took the shotgun and a Bowie knife and a baton to bushland in Mowbray where they lured Waters.

Brennan shot him in the leg and when they retreated Waters ran after them calling for help.

"When he pleaded for help you acted without mercy," Justice Pearce said.

He was stabbed and hit over the head with a baton before one said "he's not done" and fired the fatal shot into the back of his head.