Walker, who faces a two-year ban after a metabolite of the prohibited drug Nandrolone was found in a urine sample taken before Christmas, disclaims ever knowingly taking any banned substance. There have been suggestions from Walker's legal representative, Nick Bitel, that the adverse finding discovered following an out of competition test may have derived from a rogue element present in the protein compounds which the sprinter used to take.
More recently, however, scientific research from France has arisen which Bitel planned to use as part of his defence strategy. The findings by the French academic Dr Le Bizec claimed that metabolite of Nandrolone could be produced naturally by the body in raised quantities after strenuous exercise. Walker's adverse test was taken immediately after a tough training session.
Walker found out at the beginning of this month more precise details of the scientific evidence of his test. Speaking to Brendan Foster during BBC1's Athletics Focus programme, he said: "My level is slightly above the accepted level but it's the old testosterone argument again - some say you can have this level, some say you can't. We have to put enough doubt in the mind [of the panel] to show that metabolite comes from sources naturally produced in the body."
The new research was used successfully in May by the Swiss tri-athlete Oliver Bernherd, who was cleared by the Court of Arbitration for Sport in Lausanne after testing positive from the same substance.
The three-man committee, headed by QC Ian Mill, could announce its verdict at the end of today's proceedings but is more likely to retire in order to consider its decision.
According to spokesperson Jayne Pearce, it is the responsibility of UK Athletics "to show beyond reasonable doubt that a prohibited substance had been found in the urine sample. The burden of proof isn't with us to show how it got there."
The case is being presented for UK Athletics by their own lawyer, Karena Vleck, in what is described as an "inquisitorial" rather than "adversarial" fashion. The other members of the disciplinary panel are Dr Mike Turner, the former England cross-country runner, and Professor Ron Maughan, who specialises in human physiology at the Department of Biomechanical Science at the University of Aberdeen.