In his doping confessional to CBS's 60 Minutes, Tyler Hamilton not only tells of witnessing teammate Lance Armstrong's use of the banned blood-boosting agent EPO when they rode together on the U.S. Postal Service team from 1995 to 2001, but he also delivers a blow to Armstrong's longtime defense against such allegations: "Never a failed test," Armstrong tweeted in response to Hamilton's remarks. "I rest my case."

Hamilton paints a picture of a testing cover-up at the 2001 Tour de Suisse, telling CBS that Armstrong told him that he failed a drug test there. The UCI, cycling's governing body, has denied there was any such cover-up, but another former teammate, Floyd Landis, made a similar allegation last year in letters to USA Cycling as federal officials began investigating whether Armstrong was involved in a doping operation while the team was receiving sponsorship money from the Postal Service. Armstrong has repeatedly denied ever taking a performance-enhancing drug, much less testing positive for one. But if the Tour de Suisse accusations prove true, it would underscore what many in cycling have asked for two decades: Was Armstrong too big to fail?

In 1999, while Armstrong was on his way to his first Tour victory after beating cancer, a French newspaper received a tip that Armstrong had tested positive for a corticosteroid and had no therapeutic use exemption (TUE) on his medical form. Armstrong, who was riding for the Postal team, had just said in a press conference that he did not have any prescriptions for banned products. When the team discovered that the newspaper had received the tip, panic hit Armstrong and his inner-circle, according to Emma O'Reilly, a soigneur from Ireland who worked with the team and specifically with Armstrong. She was in the hotel room after the 15th Tour stage when, she says, Armstrong and team officials devised a plan.

"They agreed to backdate a medical prescription," O'Reilly tells SI. "They'd gotten a heads up that [Armstrong's] steroid count was high and decided they would actually do a backdated prescription and pretend it was something for saddle sores."

In violation of its own protocol requiring a TUE for use of such a drug, officials from the UCI announced that Armstrong had used a corticosteroid for his skin and his positive result was excused. O'Reilly also told SI that, just before the start of the '99 Tour, Armstrong asked her to use some of her cosmetics to cover up injection marks on his arm, though O'Reilly does not know what substance Armstrong had injected. O'Reilly made these same allegations in a 2004 book about Armstrong, published only in French, called L.A. Confidentiel. Armstrong subsequently filed a libel suit against O'Reilly, the book's authors and its publisher. He also sued The Sunday Times of London for reprinting the allegations in a review of the book. (Armstrong settled The Times case for an apology and recovery of his legal costs, and dropped the others.)

As early as 1993, Armstrong's testing data as a member of Team USA was aberrational. As SI reported in January, USA Cycling sent a request to the UCLA Olympic Analytical Laboratory in 1999 for past test results -- testosterone-epitestosterone ratios -- for a cyclist identified only by his drug-testing code numbers. A source with knowledge of the request says that the cyclist was Armstrong. The lab responded, detailing the cyclist's test results from 1991 to 1998, with one missing season: 1997, the only year during that span in which Armstrong didn't compete. Three results -- a 9.0-to-1 ratio in 1993, a 7.6-to-1 in 1994 and 6.5-to-1 in 1996 -- were abnormally high. Most people have a ratio of 1-to-1. Before 2005, any ratio above 6.0-to-1 was considered abnormally high and evidence of doping; in 2005 that ratio was lowered to 4.0-to-1. But the high ratios had not led to sanctions. The lab wrote that it had been unsuccessful in attempting to confirm two of the abnormal results, and the third was not mentioned. All of the tests were reported as negative. According to sources familiar with the federal investigation, the government has obtained a copy of the T/E ratio letter first reported by SI.

In August 2005, Armstrong watched his 1999 Tour de France title fall under scrutiny again when the French sports daily L'Equipe reported that his urine sample from the race, retested years later for research purposes not for sanctioning, revealed the presence of EPO. Armstrong went public and assailed the French lab for its sloppiness. Months later, Dutch lawyer Emile Vrijman, who was hired by the UCI to lead an investigation into the French lab, supported Armstrong's claim of lax record-keeping at the lab in a 132-page report. In his interview with 60 Minutes, Hamilton says Armstrong used EPO during his 1999 Tour de France victory. SI previously reported that, following the L'Equipe report, a lawyer for Armstrong was granted a private meeting with EPO experts at the UCLA Olympic lab to discuss drug-testing protocols. 60 Minutes reported that Armstrong and Postal team director Johan Bruyneel met with the director of the lab responsible for his Tour de Suisse tests.

As SI reported previously, allegations by teammates that Armstrong used EPO go back even before his first Tour win. Stephen Swart, Armstrong's teammate on the 1995 Motorola team told SI that he was on a training ride with Armstrong after a race in Italy in March 1995 when Armstrong, disappointed with the team's results, suggested the riders start taking EPO. "He was the instigator," says Swart, who admitted to using EPO after that conversation with Armstrong. "It was his words that pushed us toward doing it. It was his advice, his discussions."

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