Reporter: Charles Wooley
Producer: Danny Keens
They've been pushing their bodies to the limit, training like maniacs for their shot at sporting immortality. Now, in just a week's time, our Olympic athletes will take on the best in the world.
We'd like to think they'll be competing on a level playing field. But the sad fact is, there will always be athletes who are prepared to cheat.
Triple gold medallist Marion Jones caused a massive scandal when she admitted using performance enhancing drugs at the Sydney Games. And nowadays those drugs are even more sophisticated and difficult to detect.
So when London organisers claim these will be the cleanest games ever, Marion isn't convinced. Because with so much at stake, the cheats will always be a few paces ahead.
CHARLES WOOLEY: They're in pursuit of the Olympic dream, to go faster, higher, stronger. Their bodies are as finely tuned as any racing machine. But for some Olympians, there lies a dark temptation to use performance-enhancing drugs to win at any cost.
MARION: I think you always have to watch the Games and love it for what it is - athletes that are trying their best and trying to run faster and jump higher and all those things, but be mindful that there's that temptation, and that some of them probably have succumbed to the temptation and that's the reality.
CHARLES WOOLEY: Olympic champion Marion Jones succumbed to the temptations of performance-enhancing drugs, and today, she's seeking redemption at a church in Austin, Texas.
MARION: I decided to, as a lot of people say, come clean, tell the truth.
CHARLES WOOLEY: Now, a motivational speaker for the clean life, Marion has come a long way from the Sydney Olympics where she used a steroid known as 'The Clear'.
MARION: I returned my medals because I made poor choices. I wish I could go back and do certain things differently. I mean that's quite obvious, but if there's anybody that can handle all of this, I think it's me.
CHARLES WOOLEY: You've turned it around?
MARION: Yeah, I've had to. I've had to, I mean there's no way I could continue to live in that frame of mind, of "OK, I let the world down, I let my family down. Oh, I am just going to wallow in despair". That's not who I am, that's not how I live, that's not what led me to be a great athlete. It's just not in my makeup.
CHARLES WOOLEY: Marion's fall from grace was spectacular, but not without precedent. From the systemic doping of East German athletes in the 70s to Ben Johnson's disqualification from the Seoul Games in 1988, it's hard to remember an Olympics free from a drug scandal. So it's a bold - perhaps even foolhardy - statement by the organisers of London 2012, that they will have the cleanest games ever. Can you say that at the London Olympics, if you take performance-enhancing drugs, you will get caught?
DAVID: Yeah. Our tests are so good that we will catch the cheats. My message is to say don't take the drugs, don't cheat. Don't come to London if you want to cheat.
CHARLES WOOLEY: Professor David Cowan is chief of the anti-doping police for London 2012. His job is to catch the drug cheats, and to predict what new drugs are being abused. It seems to me a little like Coyote and Road Runner, one trying to get ahead of the other ahead of the other.
DAVID: The International Olympic Committee has asked for more tests than ever before. A good chance that half the competitors are going to be tested, and working with the sort of technologies, the latest technologies that we have at our disposal, means that we have super-fast, super-sensitive approaches that will actually catch drug cheats.
CHARLES WOOLEY: But even with the best technology in the world, the drug police know the cheats are always ahead of the game.
DAVID: So blood and urine samples will be held for eight years to allow for future advances in anti-doping technology. Samples taken at the Sydney Games were stored for just three months.
CHARLES WOOLEY: How much better is the testing now than say in Sydney?
DAVID: Absolutely amazing advances in the technologies. The equipment that may have filled a pretty large room now sits on a bench top, and yet is 10 to 100 times more sensitive than the equipment available to them in Sydney.
MARION: You have all these doping agencies now that every few months, you hear them coming out and saying they have this new technology that's going to rid the sport. Whatever - it'll be out there. Especially with the pressure that so many of these young people have of fame and fortune. It's right there in front of you, "You mean all I have to do is run fast? And all of this can be mine?"
CHARLES WOOLEY: Marion Jones is dramatic proof that you can beat the drug-screening technology. She actually tested negative at the Sydney Games, where she won three gold and two bronze medals. In the end, it was her conscience that led Marion to come clean.
MARION: And so it is with a great amount of shame that I stand before you and tell you that I have betrayed your trust.
CHARLES WOOLEY: In 2007, she confessed to misleading doping investigators - an admission that saw her jailed for six months and hit rock bottom.
MARION: I started to think everything that I had worked hard for, everything that I had accomplished would be in question.
CHARLES WOOLEY: The gold medals?
MARION: Everything. You know, I pled guilty, hoping, praying, wishing that things wouldn't be as harsh. And they were - they were probably a lot harsher than I would have ever imagined.
CHARLES WOOLEY: In fact, you were made an example of.
MARION: Some people like to say that. I mean, in essence, I guess it's the truth because I've been the only one that actually has had to serve any type of prison time for any of this.
CHARLES WOOLEY: Catching a cheat has always been hard, and it's only going to get harder. In a lab at the University of Pittsburgh, we discover a new threat to the integrity of sport - genetic doping. Professor Johnny Huard is re-engineering the human body with a science which could be used to produce a superior athlete.
JOHNNY: You are never going to take a poor athlete and bring him to the gold medallist. But you can take maybe a silver medallist and think about can I give him a fraction of a second, because the difference between the gold and silver is sometimes a fraction of a second.
CHARLES WOOLEY: Professor Huard is using stem cells to mend damaged muscles, tendons and joints - often making them stronger than they were originally.
JOHNNY: If you have a muscle injury, if you have a bone injury in sport or military, what we would like to do is harvest the stem cells, and inject this into the injured tissues to promote the repair process.
CHARLES WOOLEY: For now, it is used to treat standard injuries, but the same technology could be used to dramatically improve athletic performance. It's called genetic doping, and good luck trying to screen for it.
JOHNNY: This is your own stem cells. So if you want to test for this, that's going to become a challenge, because we take your own stem cells, that's going to be injected into you. So that's going to be your own body.
CHARLES WOOLEY: So it might be very hard to test for that?
JOHNNY: It will be very difficult, let me tell you this.
CHARLES WOOLEY: So it will be genetic doping, and you think it might be untraceable?
JOHNNY: Exactly, in contrast to steroids, that they can do some tests to look for this.
CHARLES WOOLEY: These are testing times. Dawn is yet to break, but Olympic champion Eamon Sullivan has been training for hours. For the honest athlete, there is just the hard grind. Eamon, no one can guarantee really that you won't be swimming against a drug cheat in London.
EAMON: No, there is no guarantee. I just like to think I'm racing against everyone that has the same advantage as me, which is hard work.
CHARLES WOOLEY: He's in the pool searching for something the naked eye cannot see - one hundredth of a second.
GRANT: We're just seeing how his body is travelling into the water.
CHARLES WOOLEY: There is as much technology here as the rules will allow. With the help of his coach, Grant Stoelwinder, high-tech video cameras and cutting edge computer programs, such is the mix of technologies in which Eamon invests his Olympic dream.
GRANT: 0.01 of a second will split the field. You know there are guys who missed out on the Olympic team by 0.02 of a second in this race.
CHARLES WOOLEY: So that little fraction, fraction, fraction of a fraction?
EAMON: We talk about the body reaching its maximum potential - that's when it comes down to this sort of stuff.
CHARLES WOOLEY: The reality is, few swimming records are likely to be smashed in London. The last time they were was in 2008, thanks to a spectacular advance in technology – the racing suit. With an astonishing 105 world records broken that year, they were good - so good that the suits were deemed, just like drugs, to be performance enhancers. They have since been banned.
EAMON: By the end it was pretty widely known that if you didn't have one of those suits you weren't going to win so everyone ended up getting one but I think it was a shame to see the sport go through that sort of controversy.
WOOLEY: How much more can we expect people to go faster, higher, stronger?
EAMON: I think eventually it'll get to a point that there's no further you can go, but I think there's so many undiscovered ways of training yet.
CHARLES WOOLEY: These days, Marion Jones lives in Austin, Texas, where she has recovered from the dark days of her terrible disgrace. But that's not to say she has in any way shaken off that clearly addictive competitive urge, which can turn a casual lakeside stroll into a contest. OK, so I get to say go, though.
CHARLES WOOLEY: Ready, set, go!
MARION: Do you realise that I'm wearing a dress?
CHARLES WOOLEY: OK, who made the wrong choice that time?
MARION: I am the type of individual who always wants to push myself to what some people think is the limit. I mean, I said that I wanted to win five golds before Sydney, and so many people thought I was crazy. And so at some point all of us are trying to see how far we can go. That's just how we are made up, I would hope.
CHARLES WOOLEY: Perhaps drug doping will always be the inevitable dark side of the pursuit of sporting excellence, because every competitor has one thing in common - the desire, often the obsession, to win, and sometimes at any cost.
MARION: You know, you just have to really hope for the best in terms of sport, and watch it with an inquisitive eye and knowing that that temptation's out there.
CHARLES WOOLEY: But isn't it enough to win? You guys are actually racing against yourselves, aren't you? Your own time?
MARION: No, it's not enough just to win, come on. I say that because I mean, I'm an athlete at heart, but come on, we all want to get better. It's not just - it's not just enough for me to win.
CHARLES WOOLEY: Well, it's pretty good to me.
MARION: Maybe that's what sets us apart.
CHARLES WOOLEY: Sweetheart, there's a lot of things that set us apart.