Powell , 31 , said he trusted physio Chris Xuereb , with whom he worked for only two months before testing positive for oxilofrine .
Powell , 31 , admitted he did not know the World Anti-Doping Agency 's code of conduct .
Powell , 31 , said he trusted physio Chris Xuereb , with whom he worked for only two months before testing positive for oxilofrine , and admitted he did not know the World Anti-Doping Agency 's code of conduct .