A South African prison official on Monday recommended that star Paralympian Oscar Pistorius clean a Pretoria museum for 16 hours a month as punishment for shooting dead his lover Reeva Steenkamp.

Joel Maringa, a social worker in South Africa's notoriously crowded and brutal jails, told a sentencing hearing that Pistorius should not go to jail, but receive "correctional supervision" for three years under house arrest.

Pistorius was found guilty last month of negligently killing his girlfriend in the early hours of Valentine's Day 2013.

The 27-year-old double amputee was cleared of the more serious charge of murder, a verdict that shocked the country and fuelled criticism of South Africa's legal system.

The "Blade Runner" could face up to 15 years in prison or could dodge a jail term altogether with a non-custodial sentence.

"The accused will benefit from correctional supervision," said Maringa, adding that "he will get an opportunity to restructure and modify his behaviour."

Prosecutor Gerrie Nel described Maringa's suggestion as "shockingly inappropriate."

In tough cross-examination, Nel questioned whether Maringa understood the seriousness of the crime that Pistorius had committed, after he admitted he did not have detailed knowledge of the case.

Reeva's father Barry Steenkamp held his head with his hand as Maringa spoke.

It emerged during evidence that Barry Steenkamp had suffered a stroke after Reeva's death, and her mother has repeatedly collapsed on the floor in tears, their lives shattered by the tragedy.

A friend of Reeva's, Desi Myers, expressed her disbelief at the community service suggestion, saying: "I don't want to think, I don't want to talk."

Maringa was one of three witnesses called by Pistorius's defence lawyers Monday, who are fighting to keep him out of jail.

His agent testified about his charity work and earlier Pistorius's therapist told the court that he suffered genuine remorse after shooting dead Steenkamp.

Defence witness Lore Hartzenberg said Pistorius was virtually inconsolable during initial counselling sessions after he killed Reeva Steenkamp on Valentine's Day 2013.

"Some of the sessions were just him weeping and crying and me holding him," said Hartzenberg.

"I can confirm his remorse and pain to be genuine," said Hartzenberg. "I have never found him to be anything other than a respectful, caring and well-mannered person."

She described Pistorius as a "broken man."

Nel suggested Hartzenberg was biased in favour of Pistorius, pointing out that she once cried during the trial.

"I cried in court, I was emotional once when he was required to take off his prosthesis," she admitted.

Pistorius entered the North Gauteng High Court in Pretoria amid tight security for the start of the sentencing hearing, which is expected to run for most of the week.

'Oscar's remorsefulness'

Lawyer David Dadic -- who is not involved in the case -- said the defence will "heavily expand on their trial argument regarding Oscar's remorsefulness".

"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 that could drag on for years.

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

Judge Thokozile 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, 71,000 euros).

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.

The sentencing hearing will continue Tuesday.