A convicted murderer told a former girlfriend he used a knife to kill a fisherman who has been missing for more than a decade because "the bastard wouldn't die", an inquest has heard.
The WA Coroner is investigating the suspected death of 42-year-old Mick Small who went missing in August 2001 from a commercial fishing vessel anchored about 80km north-west of Port Hedland.
The inquest today heard evidence from Lisa McDonald, who was dating one of Mr Small's crewmates, Gregory Raymond Norman, where she testified that he confessed to her that he had killed the father of one.
Norman is currently serving a life sentence with a minimum of 12 years for murdering a woman near Kalbarri in April 2005.
Ms McDonald said Norman told her that on the night of Mr Small's disappearance, he and Mr Small had stayed up drinking and they got into an argument about the way Mr Small used to speak to Ms McDonald.
He also told her he had punched Mr Small.
Ms McDonald made the allegations about Norman's confession in a statement to police in 2005.
Ms McDonald, who gave evidence by video link, said in the days after Mr Small's disappearance, Norman told her he used her car to dispose of the knife he used to kill Mr Small.
She said when she asked Norman why he had needed to dispose of a knife, he replied: "I had to have something to kill him with, the bastard wouldn't die".
Ms McDonald said Norman had also told her he got "rid of" Mr Small for her and that she "owed him".
"He whispered in my ear, it doesn't matter what you tell anyone, if I go down, you do down," she told the court.
The information came to light when police reinvestigating Mr Small's disappearance in 2005 contacted Ms McDonald.
She said she did not come forward because she had feared for her safety after Norman threatened her family and children, warning her "that if I didn't keep quiet, they'd be dead too".
Ms McDonald testified that she left Port Hedland in the weeks after Mr Small's disappearance and did not tell anyone where she was going because she was scared of Norman and she "really didn't believe that was the end of it for me".
Mr Small's sister, Debra Foskett, appeared visibly upset as she heard the details of how Norman allegedly confessed to killing her brother.
Norman is scheduled to give evidence this afternoon.