1. The fundamental evidentiary nature of the IRMS Rule is not altered by the fact that this provision precludes athletes from raising a defence based upon evidence of a physiological or pathological condition. The T/E Rule only permits such a defence because an elevated T/E ratio does not constitute direct and conclusive evidence of the exogenous administration of testosterone. There may be other physiological or pathological reasons for an elevated T/E ratio. By contrast, IRMS analysis provides direct evidence of the exogenous administration of testosterone and, accordingly, there is no place for such a defence under the IRMS Rule.