Three years later, Armstrong walked into a ballroom at the Venetian Resort Hotel Casino in Las Vegas to announce his second comeback, and he brought along two very interesting guests: On his left was the young prodigy Taylor Phinney, whom Armstrong had lured away from the vocally anti-doping Team Garmin-Slipstream. On his other side sat Don Catlin, the leading anti-doping expert in the United States, a chemical sleuth who had decoded the “designer steroids” peddled by BALCO.

As the journalists scribbled in amazement, Armstrong announced that he had hired Catlin to run a personal anti-doping program that would test him rigorously. Catlin would test for the presence of drugs, monitor dozens of Armstrong’s physical and hematological parameters to look for signs of doping, and even store samples for future testing as technology improved. “It will be the most sophisticated anti-doping program in the history of sports,” Armstrong boasted at the time. “There will be no way to cheat.”

Catlin’s presence, however, did not mean that the respected doctor believed Armstrong had always been clean. “I decided that whatever his past was, I was going to let it stay in the past,” Catlin says. In fact, more than anyone, Catlin recognized that Armstrong’s clean drug-test record proved exactly nothing.

“The assumption is that the [official] testing works, and that’s a big mistake,” says Catlin, the former director of the UCLA Olympic Analytical Lab, who now runs a private consultancy called Anti-Doping Research. “For somebody to have 50 or 100 negative tests, that’s easy, even if they’re doping. Somebody who understands how the system works can wiggle around that sort of thing.”

Most drugs leave the body quickly, within a day or so, Catlin says; only an idiot would take something longer lasting. Furthermore, it’s easy to skew test results simply by drinking lots of water, which dilutes the drugs and makes them extremely hard to detect using current tests. Lastly, the criteria for a positive test are extremely strict, with the vast benefit of the doubt going to the athlete. In many cases, he says, a sample that shows some evidence of EPO or other drugs — but is not overwhelmingly positive — will be declared clean. “As a lab you have to do that to keep the false-positive rate to zero,” Catlin says. “If we’re ever caught with a false positive, we might as well pack up.”

Translation: Plenty of athletes with drugs in their systems have still tested “negative.” One of them was a 25-year-old up-and-coming Swiss rider named Thomas Frei, who rode for the U.S.-based BMC Racing Team and tested positive in April. Unlike most who get caught, Frei confessed immediately and said he had been doping regularly for two years. His only mistake, Frei explained, was that he failed to drink enough water after the injection. “I would otherwise now be preparing for the Giro d’Italia,” he said.

In the end Armstrong’s special anti-doping program with Catlin never got off the ground. Negotiations dragged on — right into the racing season. In February 2009, on the eve of the Tour of California, Catlin, who had yet to collect any meaningful data, pulled the plug.

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