Pretoria: South African track star Oscar Pistorius had a row with a policeman who picked up his gun, after pulling over his friend for speeding.

According to the friend who testified in the murder trial on Tuesday, Pistorius had said: “You can’t just touch another man’s gun.”

Pistorius, a double amputee, is accused of murdering girlfriend Reeva Steenkamp on Valentine’s Day last year. He maintains he shot her through a locked toilet door believing an intruder was lurking in his Pretoria home.

His friend, Darren Fresco, told the court in Pretoria that he had been driving south of Johannesburg in September 2012 with Pistorius, nicknamed “Bladerunner” for his carbon fibre prosthetics, and his then girlfriend Samantha Taylor, when they were flagged down.

“Another officer went over to the passenger seat where Oscar Pistorius was sitting and he picked up a gun. There was a verbal altercation between the accused and the officer,” Fresco said.

“Pistorius said to the officer, ‘You can’t just touch another man’s gun,’” Fresco said. “Then they argued.”

After being allowed to leave, Pistorius “out of the blue” fired the gun through the open sunroof of the car, to the astonishment of Fresco, who was driving at the time.

“Apologies for my language, but I asked him if he was fucking mad,” Fresco told the court. “He just laughed.”

Pistorius had a “big love of weapons”, Fresco said, adding he knew the the Paralympic athlete “very well” and believed him to be “competent with guns” since he had grown up with them.

In another shooting incident, the 27-year-old Paralympic and Olympic star asked Fresco to take the rap on his behalf after discharging a firearm inside a packed Johannesburg restaurant.

“Being a friend I said I would, with pleasure,” the long-haired Fresco said.

Pistorius is facing separate gun charges for the two incidents, part of the prosecution’s attempts to paint Pistorius as a cocky, gun-obsessed hot-head who does not like to take responsibility for his actions. Of the four rounds he fired through the toilet door, three hit his girlfriend, a 29-year-old model and law graduate, on the hip, shoulder and head.

Earlier, state pathologist Gert Saayman had told the court that food found in Steenkamp’s stomach suggested she had eaten food at about 1 a.m. — two hours before she died and in contradiction to Pistorius’ testimony that the couple went to bed at 10 p.m.

Saayman said Steenkamp would have most certainly screamed after being shot in the arm and hip before a final shot in the head killed her. Pistorius wept and vomited several times into a bucket, as Saayman detailed the extent of Steenkamp’s injuries the previous day.

“After the first shot at the hip, screaming would have been possible, and expression of fear or anguish,” Saayman said. “It would be abnormal for someone not to scream.”

Some of Pistorius’ neighbours said in their court testimonies last week they heard a woman screaming during the shooting, but Pistorius’ lawyer insists what they heard were high-pitched cries from his client.

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

The killing has ignited debate about gun control and domestic violence in South Africa, where many women die at the hands of relatives. The bullets that killed Steenkamp were of a type that has been the subject of repeated, though largely unsuccessful, bans since the 19th century.

A pathologist, who performed the autopsy the day after she died, told the court on Monday that the fatal gunshot wounds were inflicted by a type of expanding ammunition once known as “Black Talon”.

The American-manufactured bullets, fired by Pistorius from a 9mm pistol, were banned in the 1990s in South Africa, but made their way back to the market under a different name, Ranger.

But even before that, hollow- and soft-point bullets -- also known as Dum-Dums -- were officially proscribed by the 1899 Hague Convention governing the laws of war.

“It opens up once it is inside the body and cuts the tissue,” said Jacobus Steyl, the owner of Durban-based specialist Forensic Ballistic Services. “It causes severe damage... It’s quite dangerous,” he added.

On impact, expanding bullets flare out, forming jagged edges, like flower petals.