Pretoria, South Africa (CNN) -- Oscar Pistorius killed Reeva Steenkamp on Valentine's Day last year. Of that, there is no doubt. But was it murder? One of South Africa's toughest prosecutors, Gerrie Nel, fought for most of the month of March to prove it was. Starting Monday, one of the country's shrewdest defense lawyers, Barry Roux, will try to convince a judge that it wasn't. The verdict will hinge on two questions: Did the Olympic sprinter know his girlfriend was behind the door in the bathroom of his house when he fired four hollow-point bullets through it in the middle of the night?
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The defense will try to convince a judge that Reeva Steenkamp's death wasn't murder
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Did Oscar Pistorius know his girlfriend was behind a door when he shot and killed her?
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And if he did not, did he act as a reasonable person would have?
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Experts in ballistics, pathology and psychiatry expected to try to support Pistorius' story
@placeholder needs the judge to believe not only that there is a chance he made a genuine mistake in thinking Steenkamp was a burglar, but that his response was reasonable.