Paralympic champion Oscar Pistorius has not been "putting on a show" during his murder trial in Pretoria, South Africa, a court has heard.

Probation officer and social worker Yvette van Schalkwyk told the High Court that she came forward as a witness after hearing that Pistorius had been accused of taking acting lessons.

The accusation was made by journalist Jani Allan on her blog in reference to Pistorius often breaking down in tears throughout court proceedings.

The athlete is on trial for the alleged murder of his girlfriend Reeva Steenkamp, whom he shot dead through a bathroom door at his home in Pretoria on Valentine's Day last year.

Ms Van Schalkywk was asked to assist Pistorius in his first court appearance in February last year.

She told the court: "What I saw from the first time I saw him was a man who was heartbroken. He cried, he was in mourning, he suffered emotionally. He was very sorry for the loss, especially for the parents, what they were going through."

Pistorius denies murder by maintaining that he mistook Steenkamp for an intruder when he fired the shots.