A Sydney mother asked police to lock her up. 11 days later, she was dead

Tammy Shipley walked into a police station and asked to be arrested. She just wanted to be safe.

Within days she was under 24-hour surveillance. No-one knew what they were watching.

It was just past sunset, five sleeps until Christmas, when Vicki Shipley heard footsteps approaching her front door.

She'd been finishing the cleaning up. The tree was dressed, decorations everywhere, grandkids milling about somewhere upstairs. Her nephew had just been sent out with the rubbish bins when suddenly the boy came running back inside, excited.

Moments later, two detectives were at the door. They asked Vicki to confirm her name, and whether there was anyone who could be with her for what they were about to say.

Vicki stood there in total disbelief. Then came something else. A mother's instinct.

"Straight away I understood that this didn't happen suddenly," she says. "This would have happened over days. And I wanted to know why."

In the days that followed, Tammy's family slowly began piecing together the circumstances in which she had died.

How 11 days after Tammy had gone to the police seeking protection, she died under 24-hour surveillance.

Background Briefing has spent months investigating how this was possible.

This story has confronting content and recordings of an Aboriginal person who has died. This material has been used with the permission of Tammy Shipley's family.

Tammy Shipley grew up the daughter of a woman who worked nights as a nurse and raised her largely alone. By Vicki's account, she was a talented child, one who loved playing netball and writing poetry.

"She's very academic. She was quite bright and very successful with her schoolwork," Vicki remembers. "Very athletic. She was in a team that was the New South Wales state champions."

After she grew up, she had six children who remember her caring, funny personality. Tammy made her kids laugh and smile — even when they were angry with her.

"We did a fake marriage. I was probably like five or six, and we got married and I dressed up and she put all this make-up on me."

Liam, now living in London, where he works as a professional dancer, remembers Tammy as his biggest supporter. Without her encouragement, he wouldn't have won the scholarships that got him to pursue this career.

"She just always was so like accepting of me and what I wanted to do."

But Tammy faced more than her share of challenges. Her whole adult life she had fought hard just to stay well. She had beaten cancer twice, and was diagnosed with schizophrenia and bipolar as a young woman. Medication had been effective for