The mother of a toddler found unconscious in a washing machine with his dead pet cat had a history of animal cruelty and would rip the heads off dolls as a child.
The West Australian coroner is investigating the death of three-year-old Sean Murphy, who was found in a machine on the afternoon of September 20, 2010, after his mother, Kerry, claimed she overslept.
Dianne Murphy, who adopted Kerry when she was three-years-old, told the West Australian Coroner's Court on Tuesday her daughter had been diagnosed with borderline personality order.
She said her daughter had a history of animal cruelty as a child, which a psychiatrist explained was a result of her traumatic childhood in the UK.
Murphy said her daughter had killed a frog and would often rip the heads off dolls.
"She took her anger out on her toys," Murphy said.
Constable Adam Clue testified when Sean died he overheard Ms Murphy on the phone say: "He (Sean) does this all the time. He's a little troublemaker."
He also heard Murphy say it was not her fault and she was probably asleep.
"They're treating me as a murder suspect," he allegedly heard Murphy say.
"This day just goes from bad to worse."
Constable Clue said Murphy wanted to see her son in hospital but police said she had to wait.
Neighbour Daniel Charles Dickerson testified he heard the toddler crying and Murphy telling him off in the hours before Sean was discovered in the machine.
Dickerson, who admitted being a cannabis user and being upset Murphy had put a restraining order on his son, said he had not told police what he heard because he did not want to "get involved".
But he said he had witnessed Murphy being "nasty" to her son and on one occasion, Murphy called Sean a "little bastard" when he was playing too close to a car, saying: "That car is worth more than your life."
When Sean died, Murphy told Dickerson: "I didn't kill him. It was an accident."
Dickerson denied his version of events was a figment of his imagination.
He also said he was upset the Department of Child Protection (DCP) had investigated him and had not looked at Murphy's behaviour, so he made a complaint over the counter a year before Sean's death.
The DCP's Emma White said there was no record of Dickerson's complaint and said it was not common practice to take complaints over the counter.
But White said Murphy had approached the DCP about Sean's "diabolical" behaviour, complaining Sean was like a "hurricane leaving a mess in his wake".
Coroner Alistair Hope is investigating how the boy could have accessed the machine and whether washing machine safety standards need improving.
The inquest continues.