Timothy Hemi Schaefer, 19, faced sentencing submissions in the South Australian Supreme Court today after pleading guilty to murdering Jeffrey Edwin Payne, 56, in Adelaide in April 2007.

The court was told there was no evidence he had been a victim of Mr Payne.

But in a drunken rage he punched the frail man in the nose, stabbed him in the leg, followed him across a park and taunted him about being a child sex offender before killing him, the court was told.

Schaefer's lawyer Greg Mead said his client had suffered "appalling" abuse from an early age at the hands of a violent, alcoholic father who beat him every day.

"He was fed rotten meat, that his father would have to scrape the slime off before feeding the children," Mr Mead said.

His father left his children alone for weeks at a time, at the mercy of two friends who would sexually abuse some of them.

Mr Mead said something "snapped" in Schaefer's mind the night he killed Mr Payne.

It sent him into the "primal rage" in which he attacked Mr Payne as if the man represented everyone who had ever abused the teenager, he said.

Prosecutor Jane Powell said Schaefer had never expressed any remorse about killing the man he described to police as "a sack of shit".

She said Schaefer had paused to have a cigarette during his prolonged attack on Mr Payne.

Justice John Sulan ordered a neurological report, including the effect his head injuries might have had, and remanded Schaefer in custody for sentencing at a date to be set.