World and Olympic 100m champion Justin Gatlin's legal team look set to try to prove he is the victim of sabotage or incompetence.
He faces a life ban from athletics after testing positive for elevated levels of testosterone in April.
The decision to fight the test result could be the start of a very long process.
Gatlin will use the World Anti-Doping Authority's (Wada) "exceptional circumstances" clause when he takes his case to the United States Anti-Doping Agency review board (Usada).
Former UK Sport anti-doping chief Michele Verroken has spoken to BBC Sport about the issue and explained the background to a case which could test Wada's code to the limit.
GATLIN'S DEFENCE
The Wada code means athletes are responsible for what goes into their bodies - in legal terms they have strict liability.
Gatlin is set to use the "exceptional circumstances" defence.
He can argue either "no fault or negligence", ie no responsibility on his part, or "no significant fault or negligence", ie limited responsibility.
In layman's terms, if you can prove that you could do nothing to prevent the drug getting into your body - for example, you were spiked by a rival - you could be let off with no punishment.
The "no significant fault or negligence" defence is slightly different.
If, for example, the substance was given to you by someone in your circle - a trainer, doctor or family member - you could reduce your sentence by some degree if you can show you took it unwittingly.
But as Gatlin has already failed a doping test before he could only reduce this second punishment from a lifetime ban to a minimum of eight years. Aged 24, this would end his career.
Therefore it seems certain he will try to prove he has no responsibility for the elevated levels of testosterone found in his sample.
Verroken's view: "I think it is unprecedented for an athlete facing a second offence to use this particular clause. We're in uncharted territory.
"It is safe to presume if somebody was facing a lifetime ban they're going to try 'no fault or negligence'.
"It is really about the unique facts and circumstances established by the athlete."
THE PROCESS
Gatlin's case will first be considered by the Usada's review board.
If it considers there is sufficient evidence of doping to proceed with the adjudication process then Gatlin's legal team will first appear in front of an independent panel of the American Arbitration Association (AAA).
But that may not be the end of the matter as either side can appeal against the result of the hearing.
If there is an appeal it will be heard by the Court of Arbitration for Sport (CAS) in Lausanne, Switzerland, and again either side could appeal against the decision.
Other organisations also have the right to appeal. The International Association of Athletics Federations (IAAF), Wada, Usada and USA Track and Field (USATF) could all contest the decision.
Verroken's view: "Wada has very little case law in this area. In terms of reducing penalties, the Court of Arbitration for Sport is really where the majority of the case law is building up.
"There's always a possibility that something will emerge, like an athlete changing their mind about their involvement in doping or someone coming forward and saying 'I did it'. But this could be a very long process.
"Any high-profile athlete doing this really has to take it to the nth degree because ultimately, through this process, you are building doubt into a situation where you are being labelled a drugs cheat."
ATTACKING THE CHAIN
Gatlin's legal team will have a long chain of events to challenge when it comes to the sample.
From the sample being taken, through to how it was stored, the lab it was tested in, who tested it and in what conditions, may all come under attack.
Usada is different to many other national anti-drug organisations in that it works closely with the athlete from an early stage to establish the facts and find out if there are any complaints.
Whether that makes any difference remains to be seen.
Verroken's view: "In my experience I've found that athletes have been advised to attack almost everything.
"That means from the way the test was conducted, through the chain of custody, lab analysis, management of results, the release of the data.
"There is a whole plethora of avenues that can be pursued."
THE DRUG IN QUESTION
The testosterone Gatlin tested positive for was "exogenous", which means it came from an external source.
Testosterone is a naturally occurring substance but a carbon-isotope ratio test showed the testosterone in Gatlin's system was not produced by the athlete.
Gatlin's legal team may question the reliability of the evidence, or try to prove Gatlin was not responsible for its presence, and did everything he could to not ingest it.
Verroken's view: "Testosterone cases are very, very complicated. A testosterone finding itself has complexities within it.
"It's absolutely critical to this process for the laboratory analysis to be subject to further scrutiny so you establish whether or not there is any natural reason for the result.
"It is vitally important to establish there is no other reason we can think of, at this present moment, and no scientific knowledge that would say it should not be treated as a doping offence."