'I will never be forgiven' - Patea

Lionel Patea knows he will never be forgiven for murdering his former partner Tara Brown, but doesn't want to cause her family any further pain, his lawyer says.

Patea, 25, unexpectedly pleaded guilty to murder on the first day of his trial in the Brisbane Supreme Court on Monday.

The former Bandidos bikie bludgeoned Ms Brown to death with a metal fire hydrant cover as she lay trapped in an overturned vehicle on September 8, 2015.

In a statement read outside court by his solicitor Campbell McCallum, Patea said he pleaded guilty with the full support of his family, who had encouraged him to face up to his actions.

"I do not wish to cause Tara's family any further pain nor delay their need for justice," Patea said in the statement.

"I accept without reservation the punishment imposed upon me by the justice system today, I will also be ultimately be judged by God.

"I know Tara will never be forgotten, nor will I ever be forgiven.

"I just hope that I can today stop any further potential pain and suffering for Tara's family."

Patea also said he now only lives for his daughter, who was just three-years-old when her mother was murdered.

Mr McCallum said Patea never wanted to go to trial but was not able to plead guilty until a few days ago under the advice of his legal team.

"He had always acknowledged he committed the offence," Mr McCallum said.

"He expects no leniency.

"He is remorseful, he accepts his actions and he is certainly taking full responsibility for his role in Tara Brown's death."