Western Australia’s Attorney General has issued a pardon and apology to the Yamatji family of a baby who was murdered after police arrested his mother nearly one decade ago.

In March 2013, Tamica Mullaley was violently assaulted by her partner Mervyn Bell and left naked and badly injured on the side of a road in Broome.

Police were called to the scene and arrested Ms Mullaley, who they alleged was “abusive” towards them. Bell had already fled the scene.

Her father Ted Mullaley arrived to help his daughter and was charged with obstructing arrest.

Ms Mullaley was later charged with two counts of assaulting a public officer and one count of obstructing officers.

Police agreed to take Ms Mullaley to hospital where it was found she had suffered a ruptured kidney and lacerated spleen, and left her baby Charlie with others at the scene.

Bell, who was not the baby’s father, returned and took the child.

Mr Mullaley repeatedly went to Broome police station to warn Bell had threatened to kill his grandson and urged them to search for the baby.

A Crime and Corruption Commission investigation found police took nine hours to respond to the warnings.

15 hours after Bell took Charlie, the baby was found at the Fortescue Roadhouse south of Karratha, and was pronounced dead shortly after. He had suffered horrific injuries.

In 2014 Bell was found guilty of murdering and sexually assaulting Charlie. He took his own life in prison in 2015.

Ms Mullaley was found guilty in Broome Magistrate’s Court of the three charges against her, and Ted Mullaley was found guilty of obstructing police for trying to stop them arresting his daughter.

On Wednesday, after nine years of campaigning by the family and their advocates, Ms and Mr Mullaley were pardoned by Attorney General John Quigley in parliament.

“These pardons are a show of mercy …and it has been a long time coming,” he said.

“As a government and the state, we must acknowledge that the response at the time was clearly deficient. For that, I am truly sorry. You deserved much better.

“I am sorry for the way you were treated by the government and the WA police.”

The Attorney General said he could not find a case in modern Western Australian history in which similar pardons had been granted.

In a statement, Ms Mullaley said had police treated her “like a human being” that night, her baby Charlie would still be alive today.

“I cannot express the pain that is inside me as a mother who has lost a child in such horrible circumstances,” she said.

“It never goes away, but today’s pardon and the statements in parliament are a turning point and perhaps me and my family can start to heal from now.

“It has taken nine years to be seen and heard by the WA government and it is time to look at the justice system and police that failed me and my Charlie boy.”

The Mullaley family was invited to WA parliament to hear the apology.