PRETORIA, SOUTH AFRICA—Facing allegations that he killed girlfriend Reeva Steenkamp during a dispute at his Pretoria mansion last week, track star Oscar Pistorius swore before a judge Monday that a bloodied cricket bat found on his property was in fact used in a completely different murder. “Honest to God, I never used that bat on Reeva—you have to believe me,” the double amputee said of the blood-soaked wooden paddle, claiming he had only ever used it in the 2011 slaying of a Johannesburg prostitute and “a handful” of cricket matches. “Seriously, I haven’t even seen that thing since I killed a hooker with it. To be honest, I forgot I still had it lying around.” According to sources, Pistorius went on to claim that Steenkamp’s skull was already caved in before he shot her four times.