Oscar Pistorius asked a friend to take the blame after a pistol was accidentally fired in a Johannesburg restaurant, weeks before the double-amputee runner fatally shot his girlfriend, a witness testified Wednesday at Pistorius' murder trial.

The testimony by boxer Kevin Lerena relates to firearms charges against Pistorius, and raises questions about the character of a man who insists he accidentally shot dead his model girlfriend Reeva Steenkamp in his home in the early hours of Feb. 14 last year. Prosecutors allege he intentionally shot Steenkamp.

Lerena said the restaurant shooting happened when he and Pistorius and two other friends were in a restaurant in the swank Melrose Arch area of Johannesburg in January 2013. One friend, Darren Fresco, passed his gun to Pistorius under the table and told him that there was a bullet in the chamber, Lerena said. Then a shot went off, puncturing the floor near where Lerena's foot had been, he said.

"There was just complete silence," said Lerena, who described being in shock and having blood where his toe was grazed in the incident. Then, he said, Pistorius apologized, saying: "Are you OK? Is everybody OK?"

Before the restaurant management approached the table, Lerena said, Pistorius asked Fresco to say he was responsible for the gunshot.

"'Just say it was you. I don't want any tension around me,"' Lerena remembered Pistorius saying. "'There's too much media hype around me."'

Lerena said they paid the bill and left the restaurant, and he never spoke about the incident. Two days after Pistorius shot Steenkamp, he said, he woke up to find over 100 missed calls on his telephone as media from around the world tried to contact him to ask about the restaurant shooting.

Pistorius defence critical of witnesses

Earlier Wednesday, the Pistorius' chief defence lawyer sought to undermine te testimony of a couple who say they heard screams and gunfire the night the athlete fatally shot his girlfriend, saying similarities in their accounts indicated that they had aligned their versions at the expense of the truth.

Charl Johnson, a neighbour of the double-amputee runner, had resumed his testimony on the third day of the trial after telling the court in Pretoria, the South African capital, that he heard the cries of a terrified woman and shooting around the time that Pistorius killed Reeva Steenkamp in what the athlete said was an accident in the early hours of Valentine's Day last year.

Johnson's wife, Michelle Burger, had given similar testimony and at one point broke down in tears because of what she said was the memory of the terrified screams of a woman.

Defence lawyer Barry Roux said there were differences between the statements that Johnson and Burger had given to police after the shooting, and testimony that they gave in court. Both the statements and the testimony shared similarities, Roux said, implying that the couple had contaminated their evidence by talking through what they were going to say.

"You could just as well have stood together in the witness box," Roux said. "What do you say to that?"

The tart assertion drew a caution from Judge Thokozile Masipa, who told Roux he had gone too far.

Roux contended that crucial elements in the testimony of the couple were missing in their earlier comments to police, including the statements that they heard a woman's screams rising in anxiety and intensity and that they heard the woman's voice "fading" after the last in a volley of gunshots.

Johnson suggested that he and his wife were more expressive while testifying in court than when providing information for a police document.

"I would venture a guess that it's the way you verbally tell the story," he said. "There's a lot more emotion involved ... whereas the statement is more factual."

Witness receives intimidating voicemail

At the beginning of proceedings on Wednesday, prosecutor Gerrie Nel said Johnson's telephone number had been read out in court a day earlier. Johnson then said he had since received a "large amount" of missed calls.

He described one voicemail message as saying: "Why are you lying in court? You know Oscar didn't kill Reeva. It's not cool."

Pistorius, 27, has said he shot 29-year-old Steenkamp by accident, fearing she was a dangerous intruder in his home. The case has transfixed people around the world, and the proceedings are being broadcast on television, adding to the scrutiny of South Africa's criminal justice system as well as the character of a globally admired athlete whose career peaked when he ran in the 2012 Olympics.

Pistorius was born without fibula bones because of a congenital defect and his legs were amputated when he was 11 months old. He has run on carbon-fibre blades and was initially banned from competing against able-bodied peers because many argued that his blades gave him an unfair advantage. He was later cleared to compete. He is a multiple Paralympic medallist but he failed to win a medal at the London Olympics.