A troubled woman struggled with drug addiction and several traumatic events before murdering a man in a Sydney apartment block, a court has heard.
Sharee Lorraine Turnbull repeatedly stabbed Jack Mulligan, 25, in a communal area of the unit complex in Camperdown on September 28, 2019.
The 31-year-old had a history of drug abuse that escalated around 2007 when her son died seconds after being born, the NSW Supreme Court was told on Monday.
"She was never the same again ... just lost," older sister Karla Turnbull said.
"The drug use got worse.
"When she lost her son, I lost my sister."
Ms Turnbull detailed how the sisters, born two years apart, grew up with an alcoholic mother.
That addiction escalated after Turnbull's maternal aunt was murdered by a domestic partner, leaving the kids "pretty much on their own".
The children also witnessed a relative hold a knife to their mother's throat, sexual abuse, domestic violence and "a lot" of drug and alcohol use while growing up in NSW's Central West, the court heard.
"It was just too much for any child to put up with," Ms Turnbull said.
"She really never only got the proper support she needed. I think the drug use was a way of escaping the pain and the heartache she went through."
When not drug-affected, Ms Turnbull said her sister was the "best person in the world, happy, and very protective of her friends and her family".
Mr Mulligan was found in a critical condition in the unit complex after screaming for help.
He later died in hospital.
Just four months before the fatal attack, Turnbull was released from custody on court-based parole - which applies to sentences not exceeding three years.
The hearing continues.
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