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Pistorius trial starts in South Africa

Pretoria, South Africa ( - The murder trial for South African Olympic sprinter Oscar Pistorius began Monday.

Pistorius, the double-amputee runner, shot and killed his girlfriend, Reeva Steenkamp, on Feb. 14, 2013 in the bathroom of his home. He has said he thought Steenkamp was an intruder and mistakenly killed her. Prosecutors have countered that Pistorius knew Steenkamp was in the bathroom when he fired the four shots through the door.

The trial, which is expected to last about 2 1/2 weeks, is being televised throughout South Africa and all over the world. A judge will decide guilt or innocence, as South Africa, does not have trial by jury.

Pistorius was asked by Judge Thokozile Masipa if he understood the charges against him and how he pleaded. He responded, "not guilty, my lady."

In an affidavit during his bail hearing last year, Pistorius said he heard a noise in the bathroom and, thinking it was an intruder, got his gun -- a 9-mm pistol he said he keeps under his bed for protection. He said he fired shots through the door and told Steenkamp to call the police.

When he realized Steenkamp was not in bed with him, Pistorius thought it may have been her in the bathroom. He said he called paramedics and security officers in his building complex, and tried to carry her down the stairs for help. He said she died in his arms.

In addition to the murder charge, Pistorius was charged with contravening South Africa's Firearms Control Act.

The murder charge could carry a sentence of life in prison. There is no death penalty in South Africa.

Steenkamp, who was 29 years old, was a model and reality television star in South Africa.

Pistorius, known as the "Blade Runner," made history at the London Olympics in 2012 when he became the first double-amputee runner to compete in the Games. He had both legs amputated before he was a year old after being born without fibula bones and runs on prosthetic blades.

The International Association of Athletics Federations (IAAF) had initially said that his prosthetics were considered technical aids and in violation of an IAAF rule. But the Court of Arbitration for Sport later overturned that decision, making him eligible to compete against able-bodied runners.

Pistorius qualified for South Africa's Olympic team in 2012 and competed in the 400-meter race, reaching the semifinals, and the 1,600-meter relay.

03/03 07:53:20 ET