JOHANNESBURG — South Africa's prosecutors will begin explaining Tuesday why they accuse Olympian Oscar Pistorius of committing murder in the Valentine's Day shooting death of his girlfriend Reeva Steenkamp.

Pistorius hasn't entered a plea in the case, though his family has said they strongly deny the 26-year-old double-amputee runner committed murder. They have not, however, denied outright that Pistorius shot Steenkamp, a 29-year-old model and law school graduate who is featured in a South African reality television show.

Here are some facts about the case that has shaken a nation that idolized the runner:

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THE BLADE RUNNER

Pistorius made history in the London Games last year when he became the first double-amputee track athlete to compete in the Olympics. He's known as "the Blade Runner," a nickname that plays off the high-tech carbon-fiber blades that he races on. Pistorius had both legs amputated below the knee before his first birthday because of a congenital condition, and campaigned for years to be allowed to compete against able-bodied athletes. He was initially banned because of his blades — which critics said gave him an unfair advantage — before being cleared by sport's highest court in 2008. In 2011, he won a silver medal at the world championships having been the first amputee runner to ever compete there.

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THE MODEL GIRLFRIEND

Steenkamp is a local celebrity in South Africa, known for appearing in both domestic and international commercials. She's also known for her vampy, bikini-clad photo spreads in men's magazines. She was named one of the world's 100 Sexiest Women for two years running by FHM magazine. She met Pistorius in November at a race track near Johannesburg and ended up accompanying him to a sports award show the same night, a mutual friend has said. She also was a contestant on "Tropika Island of Treasure 5," a reality television show sponsored by a milk-fruit drink now being aired on South Africa's national broadcaster SABC.

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THE VALENTINE'S DAY KILLING

In the predawn hours of Feb. 14, police officers arrived to Pistorius' home in a gated community in the suburbs of South Africa's capital, Pretoria. There, police say they found paramedics trying to resuscitate Steenkamp, whose body lay in a pool of her own blood. Police say officers found a 9 mm pistol and arrested Pistorius, who they say was the only other person in the home at the time of the shooting. Pistorius later underwent DNA testing and had samples of his blood collected. Investigators also conducted an autopsy on Steenkamp's body, though police declined to give any information about what they found. They have said she was shot multiple times in the attack. Police have not offered a motive for the killing and Pistorius' uncle Arnold later said that "the state's own case, including its own forensic evidence, strongly refutes any possibility of a premeditated murder or murder as such."

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PISTORIUS' PAST

Pistorius has had troubles in the past in his personal life. In February 2009, he crashed a speedboat on South Africa's Vaal River, breaking his nose, jaw and several ribs and damaging an eye socket. He required some 180 stitches to his face. Witnesses said he had been drinking, and officers found alcoholic beverages in the wreckage, though they did not do blood tests. In November, Pistorius was involved in an altercation over a woman with a local coal mining millionaire, South African media reported. The South African Police Service's elite Hawks investigative unit became involved before the two settled the matter. Pistorius had a fondness for guns and once tweeted about him searching his house once with a pistol, looking for an intruder.

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THE BAIL HEARING

The bail hearing Tuesday and Wednesday in Pretoria will see prosecutors offer Chief Magistrate Desmond Nair evidence about the killing to bolster their arguments that Pistorius should be denied bail and held until his trial. That evidence likely will include specific details about the killing and why they believe the athlete killed Steenkamp — things that police have been hesitant so far to release publicly. Pistorius likely will offer a plea in the case, as he didn't in a brief court appearance Friday. Pistorius' lawyers will likely try to show that he is not a flight risk and represents no danger to the community if he's free until trial. Prosecutors have said they'll pursue a premeditated murder charge against Pistorius, which could make it more difficult for him to be granted bail. Nair will hear both the prosecution and the defense, then issue a ruling about whether Pistorius will be allowed bail. That could include Nair asking Pistorius to put up cash for his release, as well as the athlete giving up his passport and setting other restrictions. If Pistorius is held without bail until trial, he will be transferred from the local police station he's currently being held in to prison, likely in Pretoria.

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JUSTICE IN SOUTH AFRICA

South Africa is one of a few countries in the world that that has a court system that takes root in Roman-Dutch law. Because of this, those appearing in criminal trials do not have the option of a jury trial, common in the United States and other countries. Instead, a single judge will hear the entire case and then rule on a person's guilt or innocence. The judge can be assisted by two advisers during the trial. Typically, those advisers offer assistance in looking at the more technical aspects of the evidence given at trial. If found guilty, a person can later appeal the ruling or the sentence they receive. A premeditated murder charge carries a minimum sentence of life in prison. There is no death penalty in South Africa.

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REACTION TO THE CASE

The day of the shooting, companies quickly removed billboards and advertising featuring Pistorius. One pulled an Internet ad for Nike showed Pistorius starting to sprint in his blades, with the caption: "I am the bullet in the chamber." Pistorius' agent was forced to cancel all the athlete's future scheduled races. Pistorius' sponsors — including big-name brands like Nike and eyewear manufacturer Oakley — are sticking by him, the agent said.