One of the men involved in the 2015 murder of Sydney police accountant Curtis Cheng says he is "happy" with his actions and an earlier declaration of remorse is "bulls**t".

Key points: During his trial, Milad Atai said he was "sorry" to Curtis Cheng's family

During his trial, Milad Atai said he was "sorry" to Curtis Cheng's family But he has since changed his mind, and now says he does not want a discount on his sentence

But he has since changed his mind, and now says he does not want a discount on his sentence He will be sentenced next week

Milad Atai, 22, has pleaded guilty to aiding and abetting 15-year-old Farhad Mohammed, who murdered Mr Cheng outside Parramatta Police Headquarters in October 2015.

A sentencing hearing is underway in the Parramatta Supreme Court for Atai, who has also pleaded guilty to two other charges for funding Islamic State.

Justice Peter Johnson said Atai was previously in the witness box for more than a day and gave extensive evidence.

In two handwritten letters sent by Atai to the Australian Federal Police and crown prosecutor Paul Maguire, he said he lied when giving evidence that he was sorry to the Cheng family and remorseful for his actions.

"I said that I'm sorry to Cheng family and about me being regretful about my action," Atai wrote.

"I would like to say I'm not sorry about my action, nor I'm regretful of my action.

"I take back what I said in the box because I was in the heat of the moment and I just slipped up.

"All praise is due to God, I'm happy with my action."

Accused doesn't want discount on sentence

Atai went onto ask that Mr Maguire tell the judge that he was not remorseful.

"If use (sic) can please let the Judge know about this letter and I want him to know where I stand with this remorse bull****.

"I have sold my life for a cheap price and that is the next life because this world is only temporary and the hereafter is eternal.

"I ask Allah to grant victory to the believers and to destroy those who oppress his slaves."

Police accountant Curtis Cheng (L) with his family. ( Supplied: NSW Police )

Atai also said he did not want any discount on his sentence for remorse.

His defence lawyer quoted a report from a psychologist who met with him after the letters were sent.

"While he continued to hold his belief system, he had 'felt for her (Mrs Cheng)' as anyone would," the report said.

The report said Atai claimed he had retracted his statements of remorse made at an earlier court appearance because he was "pissed off" with the judge.

Atai will be sentenced next week.