A policewoman has held back tears as she described in a Perth court the moment she saw a three-year-old girl's head on fire in her cot, allegedly at the hands of her father.
Edward John Herbert is on trial in the WA Supreme Court accused of setting alight his daughter and dousing her seven-year-old sister with an accelerant at the family's Doubleview home in August.
Stephanie Bochorsky was off-duty at the time and watching television in her home when she heard an altercation between Herbert and his partner.
The officer testified on Monday that when she asked the woman if she was OK, she replied: "No, he's setting the kids on fire."
Constable Bochorsky ran into the house and smelled petrol.
"Her whole head was on fire," she said, as she took a moment to compose herself.
The officer covered the girl in a blanket to put out the flames and saw Herbert pouring the liquid over the older child in her bed.
Const Bochorsky told Herbert to get away from the children, but he did not respond and remained there.
"My main concern was to get the flames extinguished," she said.
The policewoman dragged the older girl out of the bed and bolted.
Prosecutor Amanda Forrester said in her opening address of the judge-alone trial that the three-year-old was permanently scarred from the life-threatening injuries she suffered.
Ms Forrester said Herbert was a cannabis user and drinker, who was behaving strangely leading up to the incident, with his moods changing from happiness to anger.
Herbert's partner said in her statement tendered to the court that before the attack he seemed to be talking to himself and she was scared.
"I was trying to keep him calm as I was in fear for my life," she said.
She said at one point that night he told her: "The werewolf is coming at 12 o'clock."
Later, he said: "That's it bitch, I'm going to kill you."
He then said he would burn the children instead.
The woman said when she saw her burnt daughter she could "smell burning flesh" and the girl appeared to be in shock, screaming and crying.
A neighbour said in his statement that when he rushed into the house with a fire extinguisher he found Herbert drinking in the kitchen.
When he confronted Herbert, he replied: "They're my kids to do whatever the f*** I want."
Herbert then lunged at the neighbour with a knife, but the man hit him with the fire extinguisher.
Herbert has pleaded not guilty to five charges on account of being unsound of mind.
The trial continues.
AAP