PRETORIA, South Africa—The state prosecutor and lawyers representing Oscar Pistorius presented fresh evidence and questioned each other's claims Wednesday, as the bail hearing for the South African Olympic sprinter accused of murdering his girlfriend ground through a second day.

Calling on the judge to deny bail, the state brought new evidence aimed at contradicting an affidavit from Mr. Pistorius, 26, that gives his take on what happened in the early hours of Feb. 14, when his 29-year-old girlfriend, Reeva Steenkamp, was shot and killed while she was in a bathroom at Mr. Pistorius's home.

Mr. Pistorius has maintained he fired four shots through the closed bathroom door because he thought a burglar was inside. He has said he had no intention of killing Ms. Steenkamp, a model and aspiring actress.

State prosecutor Gerrie Nel said Tuesday that Mr. Pistorius "shot and killed an unarmed woman," and that he would argue the track star committed premeditated murder, a crime commanding a life sentence.

The defense has raised questions about the quality of state's evidence and the conduct of the investigation.

Oscar Pistorius stands in the dock during a break in court proceedings in Pretoria Wednesday. Reuters

The judge will decide whether to grant Mr. Pistorius bail after closing arguments Thursday.

Mr. Pistorius, whose legs were amputated when he was an infant, is one of South Africa's most renowned athletes, known as the "blade runner" for the J-shaped carbon-fiber prosthetic legs he uses on the track. He was the first disabled runner to compete against able-bodied athletes in the London Olympics.

He sat quietly through the court hearing Wednesday, as family members occasionally leaned over to rub his shoulder. He was more composed than in previous court appearances, when he sobbed uncontrollably.

But as his lawyers and the prosecutor retraced the events of Thursday morning using a diagram of his bedroom and bathroom, he broke into tears.

Chief investigating officer Botha said the shooting of Ms. Steenkamp "can't be" self-defense, adding: "I believe he knew she was in the bathroom and fired four shots in the door."

Trailblazing Athlete's Career

Mr. Botha said he arrived at Mr. Pistorius's Pretoria home at 4:15 a.m. on Feb. 14 to find Ms. Steenkamp dead on the floor on the ground level covered in towels. He said Ms. Steenkamp had been hit by a bullet on the right side of her head above her ear, on her right elbow and her right hip while she was inside the bathroom upstairs.

Mr. Botha disclosed statements from two witnesses saying they heard what sounded like a fight at Mr. Pistorius's home earlier Feb. 14. Mr. Botha said one witness, a neighbor who he said lives 300 to 600 yards from Mr. Pistorius's home, heard fighting between 2 a.m. and 3 a.m.

The state has said it was possible Ms. Steenkamp had locked herself in the bathroom following a fight. Mr. Botha said another witness heard several gunshots fired.

The chief investigator told the court that his team found two boxes of testosterone and needles, banned in many sports, during their search of the house. But on cross-examination by Mr. Pistorius's lawyer, Barry Roux, Mr. Botha said he could have misread the label and would need to see a photo to be sure.

Mr. Roux said police had found not testosterone, but a herbal remedy that isn't banned and is used by other athletes.

Mr. Roux attacked the evidence laid out piece by piece.

He also said the investigating team hadn't put on protective footwear when walking through the crime scene, suggesting there could have been contamination.

As for the witness statements, the time when they claimed they saw lights on and heard noises match what Mr. Pistorius said in his affidavit, Mr. Roux said.

Responding to a question from the prosecutor, Mr. Botha asked the court to deny bail to Mr. Pistorius, whom he said is a flight risk, citing evidence he has overseas bank accounts. Mr. Roux countered that his client has one dormant overseas account and one corporate account from which he can't draw money.

Write to Devon Maylie at