A Perth father has claimed he acted in self-defence when he fatally stabbed a DJ in his flat during an argument about drug dealing, before leaving to pick up his son from a tutoring session.

Victor Rene Amaya, 29, is on trial accused of murdering 41-year-old Jaime Fernandez — also known as DJ Suave — whose body was found under a running shower in his Tuart Hill flat in July 2016.

His body was not discovered until four days after the confrontation, when another resident of the flats reported to police that he could hear water running continuously.

Mr Amaya admitted killing Mr Fernandez, but his lawyer, Jeremy Scudds, said he acted in self-defence.

Argument over cocaine

He told the WA Supreme Court Mr Amaya had known Mr Fernandez "on and off" for many years and had tried cocaine, which he had got from Mr Fernandez, who worked as a DJ in the Perth nightclub scene.

Mr Scudds said Mr Fernandez then got his client involved in selling cocaine and, when Mr Amaya went to "catch up" with the DJ at his flat after dropping off his young son at a tutoring session, he was "confronted by an angry and aggressive Mr Fernandez".

Mr Fernandez's body was found under a running shower. ( Supplied: WA Police )

"He accused my client of stealing his customers and telling people where he lived," he said.

As Mr Amaya went to leave, a struggle ensued and Mr Fernandez produced a small flick knife.

"It turns out to be for Mr Amaya a struggle for his life. This man is going to kill him … he had got to stop the man," Mr Scudds said.

He said Mr Amaya then "panicked" and he "stupidly" moved the body into the shower and tried to clean up the scene.

Injuries appeared to be defensive wounds

The court heard he disposed of the knife, his shirt and his shoes during the journey to collect his son.

"For him, the whole situation was surreal and he was trying to disconnect himself from it," Mr Scudds said.

But state prosecutor Paul Usher said it was not accepted that Mr Amaya had acted in self-defence.

Jaime Fernandez went by the name DJ Suave. ( Facebook: Jaime Fernandez )

He told the jury Mr Fernandez had suffered eight stab wounds as well as injuries to his hands, which Mr Usher said were consistent with being "defensive wounds".

"Given the number and nature of the stab wounds there can be no doubt, he intended to kill Mr Fernandez," Mr Usher said.

The trial is expected to run for two weeks.