A South African court saw graphic images today of the bloodstained bathroom in which Oscar Pistorius shot his girlfriend, as prosecutors unveiled more details of the scene of the Valentine's Day 2013 killing.

Colonel Schoombie van Rensburg, the first policeman to arrive at the athlete's home in an upmarket Pretoria estate, described the scene that greeted him in the early hours of 14 February last year.

During his testimony, photographs of Ms Steenkamp's face and body were also shown accidentally to the court, upsetting Mr Pistorius, who vomited into a bucket for the second time since the start of the trial, now in its second week.

Col van Rensburg said that on his arrival at the home, he saw Ms Steenkamp's body lying at the bottom of the staircase covered in towels and black bags.

She had been declared dead by medics by the time he arrived.

Moments later, he found a "very emotional" Mr Pistorius in the kitchen pacing up and down.

"I asked him what happened but he didn't answer me," Col Van Rensburg told the court. "He was in tears."

The colonel said a trail of blood led him up the stairs to Mr Pistorius' bedroom and the bathroom where the athlete shot Ms Steenkamp, whom he says he mistook for an intruder.

He has pleaded 'not guilty' to murdering law graduate and model Ms Steenkamp.

Prosecutors are trying to prove that the killing was premeditated.

If found guilty of murder, Mr Pistorius faces at least 25 years behind bars.

The court was shown photos of the blood-spattered bathroom floor on which lay a crumpled, blood-soaked towel and a cricket bat that Mr Pistorius used to break down the bathroom door after shooting through it.

The photos showed empty bullet cartridges on the floor and the 9mm pistol with which Mr Pistorious fired four shots.

Ms Steenkamp was hit three times: in the head, arm and hip.

Asked by state prosecutor Gerrie Nel what condition the firearm was in, Col van Rensburg said it was cocked, with the safety catch removed.

"It's ready to fire," he said, when shown a photo. "You just have to pull the trigger."

Col van Rensburg, a police veteran of 29 years' service, was the commander of the nearby Boschkop police station at the time of the incident and had been on duty for 24 hours when he was called, he told the court.

He resigned from the police last December.

Earlier the defence team questioned the qualifications of a forensics expert in a bid to discredit key evidence from the night the athlete shot dead his girlfriend.

Barry Roux resumed questioning Colonel Gerhard Vermeulen, hoping to rubbish his testimony that could indicate the double-amputee sprinter lied about how events unfolded on 14 February 2013.

Mr Pistorius stands accused of intentionally killing Reeva Steenkamp by shooting at her through a locked toilet door, though he says he mistook her for an intruder.

His defence claims the athlete, after realising his mistake, tried to break open the door with a cricket bat.

The prosecution is positioning to argue that the couple were fighting and Mr Pistorius fired the gun after failing to beat down the door.

Yesterday, Col Vermeulen testified that Mr Pistorius was likely on his stumps when he bashed on the door with the cricket bat, contradicting the accused's account that he was wearing his prostheses at the time.

The four bullet holes and cricket bat marks on the bathroom door offer valuable ballistic and forensic evidence about the sequence of events in the case.

Mr Roux this morning attempted to show it was significant that Col Vermeulen did not have any formal qualifications to examine tool marks and did not conduct a microscopic examination of the door.

Col Vermeulen earlier admitted police may have mishandled the evidence, with footprints matching police boots appearing on the door in evidence photos, that were later rubbed off.

Mr Roux claimed they could have been from Mr Pistorius's prostheses, proving he had them on at the time the door was broken down.

He also said the door was removed from the crime scene and propped up against a cabinet and that shards of the door, which could have shone light on what happened the night of the killing, were missing.

"I did not pay attention to that stuff," Col Vermeulen said.

The admission could have far-reaching consequences for the prosecution's case.