Cole Miller's one-punch killer to find out how long he'll spend behind bars

Armstrong Renata will today find out how long he'll spend behind bars for killing Brisbane teenager Cole Miller with a single punch.

The 22-year-old punched Mr Miller in the back of the head while out in Brisbane's Fortitude Valley on January 3 last year.

The 18-year-old suffered massive brain trauma, with his family making the heartbreaking decision to turn off his life support in hospital the following day.

New Zealand national Renata pleaded guilty to unlawful striking causing death, an offence created in 2014 designed to combat alcohol-fuelled violence.

He'll be sentenced in the Supreme Court today, where he faces a maximum sentence of life imprisonment.

Due to the nature of his offence, he will have to serve 80 percent, or at least 15 years, of any jail sentence he receives.