A man convicted of murdering his brother-in-law in Perth and evading police for more than a decade has been sentenced to a minimum 17 years' jail.

Applause and cheering was accompanied by sighs of relief in the public gallery of the West Australian Supreme Court on Wednesday as Anthony Carl Prestidge was sentenced over the wilful murder of Andy Arthur Ball on September 10, 2002.

The body of Mr Ball, who died from a severe head injury, was found on September 12, 2002 under some bed sheets in his kitchen.

The 24-year-old victim had been married for four years to Prestidge's sister, Angela, and they had two children.

But the relationship was both mentally and physically abusive and Ms Ball decided to leave her husband in September 2002 - days before Mr Ball was murdered.

In her submissions to the court, defence lawyer Helen Prince said her client, who had been visiting the couple from the UK, had not intended to kill Mr Ball.

She noted both men had been drinking alcohol and the "tragic" incident happened "in the heat of the moment".

Ms Prince said her client had previously acted more appropriately by leaving the house when he was accused of having an incestuous affair with his sister.

In sentencing, Justice Lindy Jenkins said Mr Ball was prone to exaggeration and irrational belief.

Prosecutor Linda Petrusa submitted Prestidge's attack was "premeditated" and "ferocious", and showed a "callous disregard" for the victim.

But Justice Jenkins said she believed it wasn't premeditated.

Prestidge, 51, was extradited to Perth from Thailand after being pulled over for driving without a licence.

He had argued he fled because he was in shock by what had happened and could not face his brother-in-law's family.

But Justice Jenkins said she didn't accept that argument and believe Prestidge had fled to save his own skin.

Ms Petrusa said precisely what happened in the kitchen would never be known to anyone but Prestidge.

She argued that because he had just learned about the extent of the domestic abuse his sister had endured, Prestidge was after some form of retribution, so general deterrence should be a key factor in sentencing.

Justice Jenkins suggested Prestidge was "understandably in a difficult emotional position" although that did not excuse his actions.

"The law does not condone acts of revenge," she said.

Reading an excerpt from Prestidge's letter to the court, Ms Prince said: "All I can say is I'm sorry."

He also wrote that he was aware that he had caused a lot of hurt to all the family.

"I will carry this for the rest of my life," the letter read.

But Justice Jenkins said Prestidge was not remorseful and she was not satisfied he wouldn't be a threat to society when released.

The life sentence, with a minimum term of 17 years, was backdated to May 4, 2011.