REEVA Steenkamp's cousin has told the hearing for the sentencing of Oscar Pistorius that the athlete must "pay for what he's done" and she did not believe the sincerity of his courtroom apology to the family of the woman he killed.

Kim Martin, giving testimony on the impact of Ms Steenkamp's death on her family, said they are not seeking revenge for the fatal shooting, but Pistorius needs sufficient punishment.

At the court in Pretoria, Judge Thokozile Masipa has been listening to testimony from witnesses before deciding what punishment the double-amputee Olympian must serve after convicting him of culpable homicide for shooting Ms Steenkamp at his home last year.

Defence lawyers for Pistorius argued for a sentence of three years' house arrest. Prosecutors say the athlete and Paralympic champion should be sent to jail.

Ms Martin told the court: "We just feel, to take somebody's life, to shoot somebody behind the door who is unarmed needs sufficient punishment."

Pistorius was acquitted of murder for the killing, but found guilty of the lesser crime of negligent killing. Judge Masipa could order a suspended sentence and a fine, house arrest, or send him to jail for up to 15 years.

Defence lawyers have argued for a sentence of three years of house arrest with community service.

They called a psychologist and social workers, who said Pistorius should not go to prison because of his ongoing emotional suffering.

They said his disability as a double amputee who needs prosthetic legs would leave him vulnerable in jail.

Chief prosecutor Gerrie Nel has called suggestions of a house arrest sentence "shockingly inappropriate".

Ms Martin said many people had suffered because of Pistorius, including his own family, and a sentence that excludes jail time would encourage the athlete to "feel within himself that what he's done is all right".

The hearing continues.