A key police ballistics expert has said Oscar Pistorius was not wearing his prosthetic legs when he shot his girlfriend, as the athlete's trial continued in South Africa.

The police officer was giving evidence on the trajectory of the bullets that killed Reeva Steenkamp.

Mr Pistorius denies murdering the model on Valentine's Day 2013, saying he thought she was an intruder.

The prosecution says he intentionally shot her after an argument.

On day 13 of the trial, Captain Christian Mangena said analysis of the crime scene and his subsequent tests suggested that Mr Pistorius, 27, was not wearing the prostheses when he fired the fatal shots.

Correspondents say whether or not Mr Pistorius was on his prosthetic limbs when he fired his gun is important because it lends support to the defence team's insistence that the shooting was not premeditated.

Capt Mangena also said that while he had not been able to determine the exact distance, the evidence pointed to the shots having been fired from a position greater than 60cm (23 inches) away from the toilet door but no further than 3m.

Correspondents say this is in line with the athlete's testimony that he pulled the trigger while standing at the entrance to the bathroom.

Explaining the trajectory of the bullets, Capt Mangena said that Ms Steenkamp, 29, was standing up in the toilet cubicle when she was hit in the right hip by the first of four bullets.

He said she then fell backwards before being hit in the arm and the head by the last two bullets fired by Mr Pistorius through the wooden door as she crossed both hands over her head to protect herself.

'She dropped immediately'

Contradicting the athlete's testimony that the shots had been fired in close succession, Capt Mangena said there had been a short break between the first and second shots and that the second bullet missed Ms Steenkamp.

Correspondents said this corroborates evidence given by a neighbour who said she heard a shot, then a pause, then three further shots. It also suggests that Ms Steenkamp may have had time to scream before she fell to the floor, supporting the neighbour's testimony that she had heard a woman screaming.

"I'm of the opinion that after [the first] wound was inflicted… she dropped immediately," Capt Mangena said. She then slumped into a "seated or semi-seated position" on top of a magazine rack, according to the police officer.

After the third and fourth shots she "ended up with her head on top of the toilet seat, and the lower part of her body on the rack", Capt Mangena added.

But defence lawyer Barry Roux contested Capt Mangena's evidence on the timing, maintaining that the bullets could have been fired in quick succession using a "double tap" technique – where the trigger is pulled in quick succession.

Capt Mangena insisted this was "impossible", saying that if this had been the case then Ms Steenkamp's wounds would have been in the same area of her body.

The court also heard from Col Mike Sales, an officer in the police technological investigations department, who analysed data from Mr Pistorius' smartphones and tablets.

Col Sales said several websites had been browsed on the athlete's iPad on the evening of the shooting, although he could not confirm who had been using the iPad.

The internet history featured searches for used cars, including an Aston Martin and a Ford Ranger, and a free pornography website.

The court was adjourned until Monday after the prosecution said it would only call on five more witnesses.

There are no juries at trials in South Africa, and the fate of Mr Pistorius will ultimately be decided by the judge, assisted by two assessors.

If found guilty, the 27-year-old – a national sporting hero and double amputee dubbed the "blade runner" because of the prosthetic limbs he wears to race – could face life imprisonment.