A man has been sentenced to life in prison with an 18-year minimum for murdering his teenage partner in a prolonged drug-fuelled bashing motivated by jealousy.

Rodney Kevin Corbett, 30, was found guilty of murdering Colleen Ford, 18, at the house they shared in Beckenham in Perth's south-east in October 2013.

Ms Ford suffered more than 150 separate injuries, including wounds to her head, neck, arms, legs, abdomen and genital area.

She died from blunt-force trauma to her head.

Ms Ford was repeatedly assaulted between 2:00am and 8:00am, when Corbett, who was under the influence of methylamphetamine, called an ambulance.

At his trial in WA's Supreme Court, Corbett denied responsibility for Ms Ford's death, claiming he had arrived home and found her injured.

But at his sentencing hearing, defence barrister Anthony Eyres said Corbett had finally and belatedly accepted that he had assaulted Ms Ford and caused her death.

Mr Eyres said his client had told him "it's time to man-up and accept responsibility".

The lawyer submitted Corbett's motivation was "a mix of jealousy, resentment, frustration and inadequacy".

"He felt jealous of Ms Ford's relationships with others," Mr Eyres said.

The court was told the couple had been in an "on-off" relationship for about three years that Justice Ralph Simmonds described as "profoundly troubled" and marred by drug taking and violence.

In the months before her murder, Ms Ford lost an unborn child after Corbett repeatedly punched her in the stomach.

Corbett also had previous convictions for violence against another partner.

We tried to get Colleen away, family says

Members of Ms Ford's family clapped after the sentence was delivered and Corbett was led away.

One of her brothers, Danny, said the family was happy with the sentence but that nothing would bring Ms Ford back.

He fought back tears as he described her as a beautiful, happy-go-lucky girl.

"She didn't deserve to die the way she did, to a bully, to a monster," he said.

Mr Ford said the family had tried to help his sister get out of the relationship.

"The moment he started to hit her, we spent a lot of time trying to get her away," he said.

"But I guess the lure of drugs and this kind of distorted love she had for him and the promises that he made to her, she kept going back and looking for love herself.

"My advice to young women who are in this kind of violent relationship, you need to get yourself out of there because these guys are never going to change, no matter what kind of promises they make."

Ms Ford died in hospital after her mother Ruby Kickett made the decision to turn off her life support.

Ms Kickett said she missed her daughter every day but said she was happy with the court's sentence.

"It won't bring her back, I know that, but justice has been served," she said.

With time already served, Corbett will be eligible for parole in 2031.