Whether Armstrong could face a criminal charge of perjury remains uncertain. In some US states there is a seven-year statute of limitation, but it varies from state to state. Armstrong could yet face charges - which carry a possible prison sentence - if he is believed to have lied to any federal officials. In 2011, a federal investigation into US Postal - Armstrong's team - was suddenly dropped with no explanation. The authorities refused to comment on their investigation or any evidence Armstrong might have given during its course. Armstrong's legal team reportedly remain concerned over the possibility of a perjury charge.
Millar, who served a doping ban himself and is now a member of the World Anti-Doping Agency's athletes' commission, also dismissed the relevance of next week's interview.
He said: "Only Lance would get to have his moment of truth, if that's what it will be, in front of Oprah Winfrey. It is not sitting in front of a judge or a disciplinary hearing being properly questioned about the things he has done wrong. I doubt very much it will be a proper interrogation.
"My biggest concern is that it will be completely stage-managed, that he will just be 'given the ball', and that it will all be about his emotions rather than concentrating on exactly what he did wrong."
Armstrong has always denied doping but speculation that he is ready to admit his offences has grown in the US in recent days amid claims that he hopes to have his life ban reduced to allow an eventual return to competing in triathlons and Iron Man competitions. There have also been reports that his legal representatives have met with Usada, the body that compiled the exhaustive case against Armstrong which included testimony from 11 different team-mates. Then today it was announced that he had agreed to the interview to be broadcast on the Oprah Winfrey Network - it will be shown at 2am UK time and will be streamed around the world on Oprah.com.
Armstrong will not be paid for the interview, according to a statement released later by the network. It added that he will have "no editorial control" over the interview and that "no question is off limits". The network is jointly run by Winfrey's company and the Discovery Channel, which sponsored Armstrong's team between 2004 and 2007. The interview will be pre-recorded.
Armstrong is also facing claims from The Sunday Times, which is seeking around £1m after the newspaper was successfully sued by Armstrong following its reporter David Walsh accusing the American of doping, and what is known in the US as a "whistleblower" lawsuit brought by Floyd Landis, a former team-mate of Armstrong's and another doper. Landis has filed under the False Claims Act - the case surrounds the use of government money with which US Postal sponsored Armstrong's team from 2000 to 2004. The US government may yet decide to join Landis in the lawsuit.
ASO, the organisers of the Tour, have also spoken of seeking the return of around £3m in prize-money. Armstrong, who has an estimated wealth of $125m (£100m), is believed to have lost a total of £30m in sponsorship, notably through the loss of Nike's backing.
Tears on TV: Sporting confessions in front of the cameras
Paul Merson
Now working as a television pundit, the former Arsenal and England midfielder battled with a number of off-the-pitch problems during his playing career. Admitted to therapy, Merson broke down in tears during a press conference in 1995 where he confessed to being an alcoholic, a gambler and having taken cocaine.
Hanse Cronje
Former South Africa cricket captain and a national hero until he became engulfed in a huge match-fixing scandal. Received £65,000 in bribes from a bookmaker and confessed to match-fixing in 2000. Died in a plane crash before he was able to face criminal charges in 2002.
Marion Jones
The American sprinter admitted to using steroids in preparation for the 2000 Olympics. Broke down in tears at a press conference and pleaded guilty, in October 2007, to lying to federal investigators. Served six-month jail sentence.
Tiger Woods
Former world No 1 golfer confessed to cheating on his wife as he announced he would take "an indefinite hiatus" from golf. Then went in front of the cameras to apologise for his affairs at a press conference in February 2010.
Tom Williams/Dean Richards
Harlequins wing Tom Williams admitted using a fake blood capsule during a defeat to Leinster in April 2009 in order to allow a specialist kicker on as blood replacement. Williams changed his evidence at the "bloodgate" hearing and told the truth. Former Quins director of Rugby, Dean Richards, confessed "huge regret for everything" and was banned for three years.