Interview: Marion Jones' attorney Howard Jacobs

By Tom Fordyce

Jones has been under scrutiny since the Balco scandal erupted

It seemed like a case set in stone.

Marion Jones had tested positive for banned blood-booster EPO, and her glittering, Olympic gold medal-winning career was in ruins.

Or not. On Thursday, her legal team announced that her 'B' sample had tested negative, and that she had therefore been cleared of doping allegations.

How could Jones' 'B' sample not back up the 'A' sample, when both were drawn from the same single urine sample?

BBC Sport reveals all.

Two samples could possibly show different readings if Jones' urine had been mishandled or stored incorrectly.

Jacques Pruvost, a former doctor with the French athletics federation, said: "If the samples are small, you cannot find it (EPO) after a few weeks.

"It's a game of the athletes, surrounded by lawyers, to ask for the counter-evaluation ('B' test) as late as possible."

But Michele Verroken, the former head of anti-doping at UK Sport, ruled out that theory in Jones' case.

Verroken said the Los Angeles laboratories that dealt with Jones' samples are among the best in the world.

"I'm sure the US Anti-Doping Agency (Usada) will have ruled out problems with the sample," she told BBC Sport.

"I couldn't speak more highly of them. I've had the opportunity to work with them, and I know how their new set-up has really moved anti-doping issues forward."

So what really happened between the 'A' and 'B' tests?

Put brutally, the current test for EPO is not as decisive as you might think.

Introduced by the World Anti-Doping Agency (Wada) in 2003, it was designed as a cheaper and more effective version of the old blood and urine test that had come in after the Sydney Olympics in 2000.

Analysis of EPO is not simple Arne Ljungqvist IOC medical chief

Verroken says: "Anti-doping authorities knew they were losing athletes through the net, so they worked on a new detection method."

The trouble is, the new test - a urine-only one - has proved to have serious flaws.

"Wada thought it would be fine, that they had a scientifically valid method," said Verroken.

"But it seems that the scientific data can give false readings.

"The readings can imply that the EPO is man-made, when it could, in fact, be naturally occurring.

"Wada has issued a number of clarification documents, in which they've indicated to laboratories that they must get another lab to look at the results before they issue it.

"They have these safety measures in place because they started to notice that in cases where they would read the data and say, 'yes, synthetic EPO is definitely being used', naturally-occurring EPO can also be in there as an aberration.

Jones is the second-fastest woman over 100m this year

"They're saying that if the test and its assessment is properly applied, then it's valid. But they're also saying that there's room for error."

Jones is not the first high-profile athlete to fall foul of this ambiguity.

Olympic silver medallist Bernard Lagat was suspended for two months after testing positive for EPO in August 2003.

But when his 'B' sample failed to match the 'A' sample, the Kenyan-born 1500m runner was cleared.

Arne Ljungqvist, head of the International Olympic Committee's medical commission, said: "Analysis of EPO is not simple.

"You have to study the results and then you must reach a conclusion that must be clear and convincing."

Even Wada chairman Dick Pound admitted: "(The test for) EPO is open to interpretation."

Jones had not officially failed a drugs test until both her 'A' and 'B' samples tested positive.

Even then she needed to be found guilty at an independent anti-doping hearing.

The fact that her 'A' sample showed traces of EPO meant nothing unless it was backed up by the 'B' sample.

But because that first positive trace was leaked to an American newspaper, the watching world assumed that Jones was guilty.

I think the test is good - you just have to know how to read it Wada chairman Dick Pound

As her lawyer Howard Jacobs said: "They need to look at their procedures - not Usada as much as the sports federations who leak the positive tests.

"They always talk about holding athletes to the highest standards - but they need to follow their own rules."

Verroken agreed. "The confirmation of a doping offence comes after 'A', 'B', and then the hearing," she said.

"We have to suspend our judgement until all the facts have been identified and then been put before the independent hearing."

Do the cases of Jones and Lagat mean the current EPO test is now worthless - that some innocent athletes are being wrongly accused of taking banned drugs, while others are slipping through the net?

For the time being at least, Wada is sticking to its guns.

"I think the test is good," said Pound. "You just have to know how to read it."

Others are not so sure.

Verroken said: "This will do enormous damage to people's perceptions of the reliability of the testing.

"Anti-doping authorities don't want anyone to slip through the net.

"They want to be as tough as possible, but sometimes you have to be honest about where you might have a grey area so you can have the whole scientific community working with you.

"But the test has its critics, and several of them - eminent scientists - will now be saying 'we told you so'.

"We all want there to be a simple dipstick test, but we have to live with what we've got - and that makes it complicated."