Jean Pierre Morand, lawyer for FINA, has a quiet, deferential manner which contrasts perfectly with the theatrical bluster of his opponent Peter Lennon. All morning Morand sat quietly through Lennon's detailed and robust cross examination of Al and Kay Guy. Very little of what transpired interrupted his serenity. Morand was holding a strong hand of cards. He knew Michelle de Bruin's secret formula.

Just how strong the hand was made clear a few words into his cross-examination of Dr Jordi Segura, the head of the municipal laboratory in Barcelona which tested and analysed Michelle de Bruin's January 1998 sample.

"I refer to questions 25 and 27 of . . ." said Morand.

"Objection," said Lennon.

"Let him finish," said arbitration chairman Yves Fortier.

"I know what he is going to say," said Lennon.

For the following hour, in the sweltering room on the first floor of the Savoy Palace hotel where the inhabitants had voluntarily switched off the air conditioners to hear every word, we listened to the most extraordinary developments yet to take place in the none to commonplace story of Michelle de Bruin.

Lennon objected long and loud to Segura being permitted to give evidence relating to the finding of banned substances in his client's urine. The disclosure of such facts would be prejudicial to his client, especially if it were to be made public.

"But," said Morand quietly, "you knew when you begged us to have these proceedings in public what was coming."

"I never begged," said Lennon.

Argument over whether to proceed with this line of questioning ran on for the best part of an hour while Segura sat impassively with his interpreter by his side.

Morand compared the circumstance to a murder case. If in the trial in a lower court there was a certain amount of evidence and by the time the trial came to a higher court there was new evidence as to who the murderer was, it would be unreasonable not to hear that evidence.

The argument pivoted on two elements. Lennon claimed that his client hadn't been charged with having had a positive test. FINA responded that at the time of the first analysis it had only been possible to determine that de Bruin's sample showed evidence of the administration of a testosterone precursor and a decision had been taken merely to use this finding as supporting evidence in the tampering case.

Furthermore, Lennon contended that at the time of the test the substance found wasn't on the banned list and that subsequent tests had been performed illegally on the sample.

FINA were coming back for a third bite of the cherry, he said. "If the samples showed no banned substances, there was no motive."

At which point, almost simultaneously, Morand and Michael Beloff QC of CAS uttered the word which will haunt Michelle de Bruin forever.

"Androstenodione."

Andro, as it is known in the gym and locker-rooms where it is a drug of choice, is a testosterone precursor invented in East Germany by the scientist Michael Oertel.

It most recently became the centre of a public debate last year in the US when St Louis baseball star Mark McGwire broke baseball's long-standing home run record while taking the substance.

Although banned by the IOC, andro is not yet banned by baseball.

It took just a moment for the irony to sink in of the scourge of American swimmers being caught illegally taking the same substance as the hero of America's most beloved past time.

The debate on the issue of whether or not to allow Dr Segura to expand upon this topic was extraordinary for its intensity.

The de Bruin legal team ferreted furiously for supporting documentation amidst the small mountain range of material they had brought with them to Lausanne.

The decision to proceed, taking the Lennon objection on reserve and without prejudice to his client, hinged on the end on the admission by the de bruin team that an initial lab report from Barcelona dated January 1998 had indicated the presence of a testosterone precursor.

Lennon had been notified of the substance's existence in the A sample in a letter from FINA dated April 20th, 1998. All further investigations were for clarity, to identify the specific product.

"He is mixing up the definition of an offence and supporting evidence," said Morand.

Morand continued with his question.

Dr Segura performed an analysis of de Bruin's January 10th sample, five days later on January 15th 1998.

The steroid profile at the time showed the substance. During the counter-analysis of the B sample, on May 21st of the same year, Segura alleged that he attempted to show the specific data relating to the steroid profile to Lennon. He said that Lennon declined to looks at the data and would only consider information relating to alcohol and manipulation. Lennon later asserted that this was a lie.

The January 15th test was superceded by technology on February 4th when the Winter Olympics opened in Nagano, Japan. The IOC used a new variant of mass spectrometry analysis of urine in Nagano called isotope ratio mass spectrometry. Dr Segura, having observed the working of the system, applied it in Barcelona to the de Bruin sample. It told him that the unidentified testosterone precursor was in fact androstenedione.

So to the meat of Monard's controversial question. Three of de Bruin's samples from November 1997 to March 1998 showed evidence of this testosterone precursor. The highest concentration occurred in the disputed January 1998 test.

Did Segura take this as evidence that the precursor had been recently administered?

"Yes, it was taken before the sample was given, the timescale is not easy to say but results of the profile suggest it was taken in the previous 10 to 12 hours."

Did the addition of alcohol prevent you from getting an exact measure of the concentration?

"The alcohol in itself doesn't cause a problem, but indicates the sample has been diluted. The real concentration in the original could be almost double."

Monard had one last incision to make. The vexed topic of specific gravity has hung over the case since the very first press conference given in Peter Lennon's office in April 1998. The dipstick reading of the specific gravity (or density) taken by Al Guy in Kilkenny had given a reading of 1.015.

The calibrated machine in the laboratory had given a reading of .983. Lennon had inferred that this was proof that the sample which arrived in Barcelona was different to that which had been tested in Kilkenny. Segura responded that dipsticks were unreliable in cases where the sample had been subjected to something like the introduction of alcohol.

"Is it not the case Dr Segura that in Mr Lennon's presence in Barcelona on the 21st of May you tested the B sample with the dipstick method used by Mr Guy and it gave readings under different methods of 1.015 and 1.0110? The measurement in Kilkenny and in Barcelona, when effected with the same method, produced identical results."

"Yes," said Segura.

A huge blow to the tampering by a third party theory.

In supplementary questions from the arbitration panel, Michael Beloff QC formulated another question for Segura.

"If we take a hypothetical athlete, would it be in his or her interest to dilute a sample in this way?"

"Yes," said Segura.

Peter Lennon cross-examined the implacable Segura for an hour and a half, scoring no evident blows in a series of questions over chain of custody, lab procedures, chronology of testing technology and licensing. Finally, after a long day of 11 hours' evidence, the court wrapped up.

The court pointed out that there would be no pending charge of using banned substances against de Bruin, but Monard sat down quietly, his work done.

The day had ascribed both motive and opportunity for tampering to Michelle de Bruin. His opponent Lennon is left with a mountain to climb.