Perth FIFO killer jailed for 17 years

A former fly-in fly-out worker convicted of murdering a man who had a threesome with his girlfriend will spend at least 17 years behind bars.

Ryan Christopher Hawke was found guilty in the West Australian Supreme Court of murdering 50-year-old Mark Koller at the Crystal Brook Caravan Park in Orange Grove in April last year.

Hawke, 34, admitted stabbing the father of three but claimed he expected the confrontation would only be a fist fight and brought a knife with him to defend himself.

The court heard Mr Koller was repeatedly stabbed, with the knife penetrating his heart twice to a depth of 18cm and 15cm.

During sentencing on Wednesday, Hawke's defence lawyer John Prior said his client was angered when he returned home from work on an offshore oil rig and was told by his de facto that she'd had sex with Mr Koller and his partner.

Mr Prior said she had also told his client that Mr Koller had a gun and had threatened the couple.

The pair, who met during drug rehabilitation, had binged on methylamphetamines, heroin, benzodiazapines and alcohol for eight days in the lead-up to the attack.

While he hadn't taken drugs that day, Hawke was affected by a substantial amount of alcohol when he made a last minute decision to take a knife as he left his caravan.

"It was a spur of the moment decision to arm himself with the knife," Mr Prior said.

"There was no intention to kill the deceased before he left the unit. Events escalated very quickly."

The court heard the victim had fought back during the incident, which lasted no more than 10 minutes.

Before Hawke fled the scene, he bent over and apologised to Mr Koller as he lay on the ground bleeding.

Hawke, a father of four, also said "I'm sorry" as he was led out of the courtroom following his guilty verdict.

Justice Ralph Simmonds concluded that Hawke was remorseful and had formed intent to kill on the spur of the moment, but it was a serious case of murder.

Hawke, who has already been in jail for about a year-and-a-half, must serve a minimum of 17 years behind bars before being eligible for parole.

Speaking outside court, the victim's brother Michael Koller told reporters he hoped Hawke would use his time in prison to reflect on his actions and rehabilitate himself.

"There's no winners in this - his family is destroyed just as much as ours is," Mr Koller said.

"It's a tragic situation. Again, drugs has risen its ugly head."