Fallen Paralympic hero Oscar Pistorius returned to court Monday, with his top-flight legal team expected to argue for a non-custodial sentence after his conviction on the equivalent of manslaughter charges.

The double-amputee track star was found guilty of culpable homicide, but cleared of premeditated murder in killing his girlfriend Reeva Steenkamp, a verdict that shocked the country and fuelled criticism of South Africa's legal system.

Amid tight security, the 27-year-old entered the North Gauteng High Court in Pretoria for the start of sentencing, which is expected to run for most of the week.

The "Blade Runner" could face up to 15 years in one of South Africa's notoriously brutal prisons or could dodge a jail term altogether with a non-custodial sentence, given that he was found not guilty on the most serious charge.

Kicking off the process, the defence team will bring mitigation arguments before Judge Thokozile Masipa.

They are likely to argue that the country's prisons are not suited for his disability and that the 2012 London Paralympics silver medallist deserves leniency as a first time offender.

Lawyer David Dadic said the defence will "heavily expand on their trial argument regarding Oscar's remorsefulness" in killing his girlfriend of Reeva Steenkamp.

"The biggest factor, however, which the defence will raise is, of course, the fact that Oscar is a first time offender," he added.

In turn, the state will call witnesses to testify on why he should serve the stiffest penalty, raising the issue of his history of negligence with firearms.

After the sentence is handed down, both the state and defence can appeal, a legal process likely to drag out for years.

In September, Judge Masipa ruled the 27-year-old did not knowingly shoot to kill 29-year-old model and law graduate Steenkamp on Valentine's Day 2013.

The sprinter admitted he fired four hollow point bullets through a locked toilet door in his upmarket Pretoria home, but said he believed he had been shooting at a burglar.

Masipa's ruling outraged many South Africans, including lawyers who believed she misinterpreted the definition of murder, and questioned whether the justice system is failing the crime-plagued country.

Pistorius is currently out on bail of one million rand ($90,000). He had to sell his posh house inside a gated compound in Pretoria, the scene of the crime, to fund the cost of the trial, and has withdrawn from competitive sport since his arrest.

The trial which began on March 3 was broadcast live on television and radio, feeding insatiable local and international media interest.

The athlete cut a lonely figure in the dock, at some points sobbing and retching loudly while testifying.