lance armstrong is a liar? >> yes, i suppose if that's the question, yes. >> landis is a confess eed perj record and a liar. >> reporter: armstrong's attorney told us lance has never cheated. >> lance is the most tested athlete, amateur or professional, in the history of sport it's around 300 separate tests that he's undergone. and he has never had a positive test. as we say in texas, the prooch's in the pudding. >> reporter: the blood between landis and lance armstrong wasn't always so bad. landis was his faithful lieutenant and eventually his heir apparent. when armstrong retired with seven tour wins in 2005, landis took up the charge, winning the tour de france in 2006 and becoming a hero in the process. >> floyd landis, now, can take time out. he is the winner of the 93rd evident. >> reporter: the adoration didn't last long. he was soon accused of using performance enhancing drugs and found guilty. a charge he would fight, in press conferences, on television -- >> yes or no, did you use drugs to win the tour de france? >> no, robin, i did not. >> reporter: and in arbitration hearings. armstrong himself was a landis supporter at the time. >> my suggestion to floyd would be to, if you believe you're innocent, you stand up and fright for it. >> reporter: landis even wrote a book to say he never used doping products, and he wrote, armstrong was clean, too. so, why would anyone believe landis now? it is a question u.s. federal investigators