A self-confessed killer told police his relationship with his victim, whose head washed up on Rottnest Island, was like a father and son, the Perth Supreme Court has heard.

Aaron Carlino made the comments in a recorded interview with police, in January 2013, three weeks after he shot 56-year-old Stephen Cookson in the head and dismembered his body.

Carlino has admitted to killing Cookson but denied it was murder, claiming he acted in self-defence because Cookson had subjected him to months of physical, emotional and financial abuse.

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The two shared an apartment in East Perth and in the interview Carlino described their association as “like a family relationship”.

“At first it was meant to be a business relationship, but it turned into a father-son relationship, where I did what he said,” Carlino said.

He denied their relationship was sexual.

When asked why he killed Cookson, Carlino said it was because he wanted to get away from him.

“I was forced against my will to stay there,” he said.

“I didn’t want to work for him, I didn’t want to live there, but he kept me there, he wouldn’t let me go.

“I was scared of him.”

Carlino said Cookson had never inflicted any serious physical injuries on him but had “more of an emotional sort of stronghold” over him.

“It was coming to a stage where it was clear it was going to end badly,” Carlino said.

Prosecutors told the court they rejected Carlino’s claim of self-defence, and maintained Cookson’s killing was “cold blooded, premeditated murder”.

The court heard that after shooting Cookson twice in the head as he slept on a sofa, Carlino used a knife and an angle grinder to cut his body into six pieces.

The body parts were initially buried at a property at Golden Bay, south of Perth, before they were dug up and dumped at sea.