Anything but a prison sentence for Oscar Pistorius for shooting dead his model girlfriend Reeva Steenkamp would be "shockingly inappropriate", prosecutor Gerrie Nel has said.

He resumed his relentless cross examination of probation officer Annette Vergeer, a defence witness, who on Tuesday told the athlete's sentencing hearing that Pistorius would be "broken as a person" if he was jailed.

Mr Nel said to place the runner under house arrest and sentence him to community work for three years as she had recommended would be "too light" a punishment.

The prosecutor also raised the prospect of a public backlash if the sentence for the double-amputee Olympian was not harsh enough, saying the court had to guard against people "taking the law into their own hands".

"Our courts and society value human life," he told Ms Vergeer, and asked her: "Don't you think society wants a heavy punishment?"

"You're recommending house arrest... but the accused could be allowed to pursue his athletics, train, find a job and go to work and return to his house..."

"That this accused be sentenced to three years correctional supervision, with 16 hours a month correctional duties is shockingly inappropriate. It cannot even be considered," Mr Nel said.

The 27-year-old was convicted last month for killing Ms Steenkamp on Valentine's Day, 2013.

Ms Vergeer, who was paid by the defence to produce her report, said Pistorius would be vulnerable to violence and placed in highly stressful situations because of his disability.

"The death of the deceased and the period since have been a far bigger punishment than incarceration," she said.

The case continues: