A man who murdered his partner during a sex game has been confronted by the victim's father in an Adelaide court.

David Richard Fraser pleaded guilty part way through his trial to murdering Luke Noonan at a West Beach flat in Adelaide in 2009.

The court heard Mr Noonan was participating in a consensual sex game and Fraser tied a belt around his neck, but persisted after Mr Noonan lost consciousness.

It is the second time Fraser has been convicted of such a crime.

He served a sentence for the manslaughter of another man who was strangled with a shoelace during sex more than four years earlier.

Mr Noonan's father, Michael, read a statement to the court during sentencing submissions, telling Fraser he should never be released back into the community.

"You must never ever be given the opportunity to commit such a crime again," he said.

"You had previously been given the chance to mix into society and this resulted in the murder of my only son.

"The only just thing would be to prevent you from mixing with society for the rest of your life."

The victim's sister, Emma Linsenmeier, said she feared people may judge her brother unfairly because of his lifestyle.

"He came from a home filled with much love and stability, he never hurt anyone, he was a gentle but lost soul," she said.

"He did not deserve to go this way."

A family friend of Luke Noonan also conveyed her anger in the court.

"To me David Fraser you are worth nothing," she said.

"There are not enough words to describe what you have done to this family.

"I, with other taxpayers, will be keeping you in comfort and security. You make me sick."

Fraser's lawyer, Bill Braithwaite, described the killer's life as terrible and sad.

He told the court Fraser suffered intellectual and social disabilities and had the cognitive ability of a nine-year-old.

He said Fraser had an abusive upbringing, was humiliated at school and turned to prostitution at an early age.

"It was a dreadful life," Mr Braithwate told the court.

"There are two stories here and Fraser's story is a terrible story and one can see his slide into alcoholism and depression within the terrible lifestyle he lived.

"He did regard Luke as a friend and he does understand the suffering he has caused."

Prosecutor Sandi McDonald said the crime must be seen in the context of the earlier offence

"[This is] someone who has only a couple of years before strangled another person that he cared for and thought of as a friend in exactly the same circumstances."

She said Fraser had panicked and failed to call an ambulance to get help.

"If at any of these stages this man could've survived, the prisoner deprived him of that chance," she said.

Justice Margaret Nyland will sentence Fraser later.