AUSTIN, Texas (AP) -- Lance Armstrong faces a Friday deadline to file a formal response to the latest allegations that he was doping during his seven consecutive Tour de France victories.
The U.S. Anti-Doping Agency informed Armstrong on June 12 that it plans to bring charges that he used performance-enhancing drugs. If found guilty, Armstrong could ultimately be stripped of the Tour de France titles he won from 1999-2005.
Armstrong insists he is innocent and despite the deadline he isn't required to file a written response. The deadline is important, however, because now the case will be sent to a USADA review panel to determine whether there's enough evidence to warrant formal charges.
If it does, Armstrong could find himself before an arbitration panel to decide the matter by November.
Here's a look at a few of the questions surrounding Armstrong's case:
Armstrong hoped the end of the criminal investigation would end the doping questions. The latest allegations are that he used blood boosters, steroids and other improper performance enhancers and violated sports competition rules, not criminal law. Armstrong can't be put in jail if he's found guilty, but he can be stripped of his titles.
When the federal criminal probe ended, USADA officials warned they would continue investigating Armstrong and their level of proof required when presenting evidence is lower than the legal standard of "beyond a reasonable doubt." USADA officials insist their standard of proof is still very high.
Armstrong had suggested in recent interviews he expected charges to be filed and even hinted he may not fight them, saying he was tired of the battle. That would seem unlikely now given his tenacious determination to fight off previous doping allegations during his career.
The U.S. Olympic Committee recommended creating the agency because its own drug-testing program lacked credibility. USADA is supported financially by the U.S. Olympic Committee and the federal government.
Part of USADA's mission is to not only catch cheaters but to help researchers create new, more sophisticated tests to keep up with evolving cheating techniques.
From his Tour de France titles to his legacy as the cancer-fighting hero to his foundation that trades on his name to raise millions of dollars to help cancer survivors, it's all on the line.
After his 1999 Tour de France victory, Armstrong wrote a book, "It's Not About the Bike: My Journey Back to Life," that helped define him as an inspirational athlete who came back from the brink of death to beat cancer and dominate a grueling sport. Now he allegedly faces evidence that could taint his entire career on the bike.
Armstrong also has legions of fans around the globe due to his work fighting cancer. They may not care about doping in sports. But a formal ruling that he's a cheater, that it's not just innuendo and rumor, could be devastating and a disappointment for many.
USADA hasn't released witness names or the blood samples, despite a demand from Armstrong's attorneys to see them. USADA says it's keeping the names private to prevent retaliation or intimidation, raising speculation Armstrong will file a federal lawsuit to gain access.
Armstrong notes he's passed about 500 drug tests in his career. And in a letter to USADA last week, his attorneys noted the blood samples that allegedly indicate doping came from a time Armstrong passed all his drug tests.
Unlike other sports figures who have been sanctioned after positive drug tests, USADA's case against Armstrong appears to be built around the total weight off the alleged witness testimony and suspicious blood samples.
Presuming the case proceeds, it goes to a three-person arbitration panel. Armstrong picks one member, USADA picks another and those two arbitrators pick the third, who acts as the panel chairman. Once that happens, USADA will have to start turning evidence over to Armstrong and his lawyers to review.
Armstrong can contest the charges or accept them. If he challenges USADA, the case goes to a hearing before the arbitration panel where both sides can present evidence and cross-examine witnesses. Armstrong can elect to have an open hearing or keep it closed to the public.
Only one athlete, former cyclist Floyd Landis, a former Armstrong teammate who won the 2006 Tour de France and later tested positive for steroid use, chose to have an open hearing and he lost. He later became one of Armstrong's primary accusers.