Reeva Steenkamp's mother, June Steenkamp, forgives Oscar Pistorius but does not believe his story

Reeva Steenkamp's mother says she has forgiven Oscar Pistorius but does not believe his story about what happened on the night her daughter was killed.

Prosecutors have been granted leave to seek a murder conviction against Pistorius, who is serving five years' jail for culpable homicide, the South African legal system's equivalent to manslaughter.

Pistorius, an Olympic and Paralympic track star, shot dead Reeva Steenkamp through a locked toilet door at his home in South Africa on Valentine's Day last year.

Throughout his seven-month trial, Pistorius maintained that he shot Steenkamp, who was his girlfriend, by mistake, thinking she was an intruder.

June Steenkamp said she believed the truth was still to come out.

"I've forgiven him, but I will never forget the way he killed my daughter," she told the ABC's 7.30 program.

"She must have been petrified. She was in a small, little cubicle. She couldn't move to get away from those bullets."

June Steenkamp said Pistorius had used black talon ammunition, which explodes in the body.

"She could never have lived through that, or any other person that he thought was in there," she said.

"Even if he thought it was a burglar, they would also have been dead. It was still a killing."

Ms Steenkamp said she would also be paying back the money Pistorius gave her in the wake of her daughter's death.

"All that money is going back to him in any case. I decided every single cent is going to go back to him," she said.

"My lawyers are busy with that right now. That money is going back. I refused three amounts.

"I said I don't want that money. I don't want blood money. My daughter was priceless."

When asked why she accepted regular payments of a few of hundred pounds a month, Ms Steenkamp replied: "Because we were bankrupt."

"They came to us with the offer to pay our rent. And the civil case was already in paper work and we were going to do the civil case and then that money would come out of the civil case. When we were destitute we didn't have an alterative," she said.

"I don't think anybody's got the right to judge the decision that I made.

"I'm not going to feel ashamed for that because we didn't have a choice."