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Would we think differently about an athlete if they had been taking supplements unknowingly contaminated with banned substances? The Jamaican sprinter Asafa Powell recently served a six month doping ban - which he argued came from a tainted supplement he took in good faith So when is doping deliberate and when is it unintentional? Should we have any sympathy for athletes like Powell? Sportshour's Sarah Mulkerrins has been looking at how big an issue it is PHOTO: Asafa Powell at the London 2012 Olympics CREDIT: Cameron Spencer/Getty Images