Seven-time Tour de France champion Lance Armstrong faces controversy in the twilight of his career. (AP)

Cyclist Lance Armstrong is  facing a federal investigation examining allegations that he organized blood doping on the US Postal Service team between 1999 and 2004. Armstrong has vehemently denied ever using performance enhancers. In their article, “The Case Against Lance Armstrong” in the current issue of Sports Illustrated, reporters David Epstein and Selena Roberts examine the accusations against the  seven-time Tour de France winner. Bill talks with Roberts and Epstein about previously unreported information they uncovered.