Perth dad set daughter alight because she was 'too beautiful'

A Perth father has been sentenced to 17 years in prison after setting his own children on fire while high on drugs.

Edward Herbert attacked the girls, one of whom he set on fire, at the family's Doubleview home in August 2015.

He said he set one of his daughters on fire because she was "too beautiful".

Edward Herbert has been sentenced to 17 years in jail for attempting to kill his two daughters. Source: 7 News

He soaked the defenceless toddler in petrol and then set her head on fire.

His seven-year-old daughter was targeted next.

The little girl, who has autism, had fuel thrown on her while her mother screamed for help.

An off-duty policewoman, Stephanie Bochorsky, heard the screams and came running to help.

Stephanie Bochorsky, left, came rushing from a nearby house to help. Source: 7 News

She ran inside and threw a blanket on the little girl on fire before getting the children away from their father.

Before walking into the room with a jerry can, Herbert had chased the children's mother with a knife and threatened to kill her and blow up their home.

Herbert paced around the house with a jerry can, threatening to blow it up. Source: 7 News

A heavy marijuana and alcohol user, he wrote a letter to Supreme Court Justice Lindy Jenkins saying "he had no idea his use of cannabis would affect his mental state."

Edward Herbert was smoking cannabis and drinking heavily in the weeks leading up to the attacks on his children. Source: 7 News

He had reportedly been drinking almost a carton of beer and smoking $50 worth of cannabis a day in the weeks leading up to the attack.

Justice Jenkins rejected his insanity plea in April this year.

While accepting he showed remorse, she jailed him for 17 years.

Herbert will never be allowed to see his daughters again but can see his son two years after his release from jail. Source: 7 News

In court the trauma suffered by the children and their mother was described as "long-lasting."

His youngest daughter suffered burns to 13 per cent of her body and the attack has left her permanently scarred.

She has also suffered damaged vocal chords and hearing.

Herbert has been banned from contact with his daughters and ex-partner under lifetime restraining orders.

His son, who was not attacked during the drug-induced rampage, will be allowed to see his father two years after his release from jail.