A man who brutally assaulted a gay lover, set fire to his apartment, then left him to suffer fatal burns on top of fatal head injuries, has been jailed for life with a minimum period of 20 years.

Lane Tynan Mitchell, 25, punched, kicked and bludgeoned Peter Anthony Jarman with a wine bottle and a statue at the 49-year-old’s North Perth apartment in June last year after they had sex, took methamphetamine then had an argument over cash.

New Zealand-born Mitchell, a father-of-two who provided the drugs, claimed he became angry when Mr Jarman refused to give him cash for a taxi fare, but Supreme Court of WA Justice Bruno Fiannaca said that was unfathomable.

Mitchell took Mr Jarman’s wallet and demanded his PIN, and it was more likely he was furious the older man refused to help pay for the $1000 worth of meth they had taken.

In any event, Mitchell took an Uber to flee the burning apartment minutes after starting the blaze by setting fire to one of Mr Jarman’s tops using fly spray.

Mr Jarman was unconscious when Mitchell left and suffered full-thickness burns to more than 50 per cent of his body in the fire, which caused an explosion that blew out the bedroom window and damaged nearby units.

It also left $250,000 worth of damage to the apartment block’s common areas and threatened the lives of others including firefighters, who retrieved Mr Jarman’s battered body from a dark blanket of smoke.

The court heard Mitchell claimed he put Mr Jarman’s computers in the shower and turned on the water after looking up how to restore factory settings because he wanted to erase any evidence of their trysts.

He also claimed he set fire to the clothing as a threat to his victim in a bid to make him reveal his PIN.

But Justice Fiannaca said Mitchell intended to destroy any evidence that linked him to the murder, which he’d formed an intent to commit when his anger over Mr Jarman’s defiance escalated to a meth-fuelled rage.

He described the crimes as ferocious, merciless, callous and appalling, saying Mitchell showed no remorse.

Mitchell had no character references because he didn’t want his family to know about the sentencing, where they would learn he’d had gay sex.

Justice Fiannaca said it was astounding the former state-level rugby player was more ashamed of his homosexual relationship with the victim than the taking of his life.

Mitchell was emotionless when he was sentenced on Friday via video link from jail, sitting with his arms folded and only saying “yep” when he was spoken to.

© AAP 2018