Three urine samples taken from the Irish swimmer Michelle de Bruin between November 1997 and March 1998 showed positive signs of use of the banned testosterone precursor and rostenedione, the Court of Arbitration for Sport (CAS) in Lausanne heard yesterday.

The Court is hearing de Bruin's appeal against a four-year ban imposed last August for her alleged tampering with a urine sample provided on January 10th, 1998.

Dr Jordi Segura of the Municipal Laboratory in Barcelona testified that the sample taken from de Bruin on January 10th, 1998, which is the subject of the current tampering case unfolding before the court, had a higher concentration of the drug than the other samples, leading him to believe that the drug had been ingested sometime in the previous 10 to 12 hours.

Segura said that the drug was on the banned list at the time and that he had notified the swimmer's legal team of the presence of a precursor in his initial lab report. He also claimed that at the opening of the B sample portion last May, de Bruin's solicitor Peter Lennon, declined to view any evidence relating to this.

Lennon replied that this was a lie. Michael Beloff, one of the court's three judges, later interjected that it would be a normal thing for a lawyer to try and eliminate damaging elements of a case. Lennon said he would produce letters today that will show that he had earlier been seeking from FINA the very evidence which Segura claimed that he dismissed. The only such letter he was able to produce in court yesterday was dated June 18th, 1998, almost a month later.

Segura said that he had advised FINA not to proceed with a charge of use of a banned substance because at the time of his first investigation of the relevant sample in January 1998, he had only been able to determine that the drug was a precursor of testosterone, namely a drug designed to promote the growth of testosterone in the body. He was unable to identify the specific brand and advised that the evidence be used to support a charge of tampering.

Soon afterwards new technology enabled him to identify the drug, but at the time the International Olympic Committee (IOC) advised that the new technology could not be used alone to support a case of use of a banned substances.

In a marathon day of testimony, Segura's evidence was easily the most dramatic and potentially fatally damaging to the hope of de Bruin having her case overturned. Lennon lodged a multi-layered legal argument in an attempt to prevent Segura discussing any finding not relating to the presence of alcohol in the January 10th sample, but failed to have the cross examination so narrowed.

Lennon had previously asked the Court to hold the proceeding in public.

Earlier cross examination had centred on a microscopic examination of all that happened on January 10th, 1998. In turn, Michelle de Bruin, Al Guy and Kay Guy took the stand and, under pain of perjury, gave their painstaking accounts of those events.

Testimony conflicted, but none of the three appeared to suffer any terminal blows to their credibility.

The case continues today with evidence being provided by Staffan Sahlstrom, chief executive of International Doping Tests and Management, and Jeff Hutton, head of the doping control division of Versapak, the company who makes the containers in which the urine was stored and sealed. The de Bruin defence is expected to hinge on questioning the reliability of the Versapak kits and evidence is also expected from Dr David Brown, the scientist who claims the kits can be opened by boiling them and using a kitchen knife.

A decision on the case is expected later in the week.