Photo of dead Reeva Steenkamp shown to Oscar Pistorius during cross-examination

South African Paralympic champion Oscar Pistorius became distraught as he was shown a photo of his dead girlfriend Reeva Steenkamp by the prosecution at his murder trial in Pretoria.

“It’s time that you look at it,” chief prosecutor Gerrie Nel said, presenting the photo at the start of the first day of cross-examination.

Oscar Pistorius, who denies murdering Reeva Steenkamp, insisted he had made a “mistake”.

The athlete says he accidentally killed his girlfriend after mistaking her for an intruder.

He told the court on Wednesday: “I made a mistake. My mistake was that I took Reeva’s life.”

Prosecutors say Oscar Pistorius intentionally killed Reeva Steenkamp on Valentine’s Day last year by firing a gun through a bathroom door at her after a row at his Pretoria home.

Oscar Pistorius, who is a double amputee, faces life imprisonment if convicted of murdering the 29-year-old model, reality TV celebrity and law graduate.

Following legal arguments on Wednesday morning, Gerrie Nel showed video footage of the athlete at a gun range shooting a watermelon.

Gerrie Nel then said the watermelon had exploded in the same way as Reeva Steenkamp’s head – and showed the photo. He asked Oscar Pistorius to look at it and take responsibility for his actions.

An emotional Oscar Pistorius, 27, turned away from the image on a monitor screen and said: “I’ve taken responsibility… but I will not look at a picture where I am tormented by what I saw and felt that night… I remember. I don’t have to look at a picture, I was there.”

After an adjournment to allow Oscar Pistorius to compose himself, Gerrie Nel sought to highlight what he said were inconsistencies in the athlete’s statements, questioning his claims that police had tampered with items in his home after the shooting.

“I am not pleading not guilty because the scene was contaminated,” Oscar Pistorius countered.

“I am pleading not guilty because what I’m accused of didn’t happen.”

In the opening moments of cross examination, Gerrie Nel showed the highly combative style Oscar Pistorius can now expect from him in the coming days.

Earlier, while being questioned by his lawyer Barry Roux, Oscar Pistorius told the court he had tried to revive Reeva Steenkamp, who was hit by three of four pistol rounds he fired through the door.

He said he had managed to carry Reeva Steenkamp downstairs, where neighbors had tried to administer first aid before paramedics arrived.

Before Barry Roux ended his questioning, he asked Oscar Pistorius if he had intentionally killed Reeva Steenkamp.

“I did not intend to kill Reeva or anybody else for that matter,” he replied.

If Oscar Pistorius is acquitted of murder, South African law stipulates that the court must consider the separate, lesser charge of culpable homicide, or manslaughter, for which he could receive between six and 15 years in prison.