The mother of a man brutally murdered while walking in Canberra's CBD has called for the death penalty for his two attackers.

A 19-year-old man, referred to as JJ, and Taylor Lewis Schmidt, 22, beat Liang Zhao to death with a baseball bat and machete as he was walking home from a bus stop along Northbourne Avenue in August 2011.

JJ was 17 at the time of the attack and therefore his full name cannot be published.

He and Schmidt pleaded guilty to the murder just days before their trial was due to begin earlier this year.

Today, JJ again faced the ACT Supreme Court for his sentencing hearing.

His lawyer read out a letter that JJ had written that morning to Justice Richard Refshauge.

"I'm writing this letter to you because I'm too ashamed to write to the victim's family," he wrote.

"I'm so sorry for what I did and who I hurt.

"Sometimes the pain is so bad I wish I could take his place, but I can't."

Hate and pain 'cannot be described in words'

Mr Zhao's mother, Giufu Min, was also in court briefly before she broke down and had to leave, but a member of the victim's support team read out a letter she had also written.

"Our son left home strong and healthy and returned in a box," she wrote.

"The money we reserved for Liang's wedding was now used for his funeral."

She said the pain and hate she felt could not be described in words.

"I wish I could have killed the murderers myself and smashed them to pieces," she said.

"They should pay for this bloody death with their lives."

Victim killed for $21 and mobile phone

She also called on the ACT Government to explain how such a crime could happen in the national capital and asked them to establish a safe area for people to wait for buses in the CBD at night.

"Why wasn't the bus waiting room open?" she wrote. "If it was open he would still be alive."

Ms Min then took issue with racism in Australia.

"We are all Australians. If you want to kill Asians because you don't like us, is it OK for us to kill you?" she said.

But JJ took to the witness stand to explain that he never intended to murder Mr Zhao and the pair had only planned to rob him.

They stole $21 and his mobile phone.

The teenager will be sentenced next month.