The blue magic doping scandal involving some of New Zealand's top racing names - two of whom have since died in suspected suicides - was finally played out before a judiciary yesterday.

Canterbury trainer Mark Purdon pleaded guilty before the industry's Judicial Control Authority (JCA) in Christchurch to acting in a manner detrimental to the interests of harness racing.

He admitted administering a "substance" to Light And Sound on two occasions, despite authorities not finding any positive swabs when the horse was tested.

Purdon told police and Harness Racing New Zealand (HRNZ) last year he administered a substance but said he did not know what it was.

The JCA will deliver a written decision on a penalty in two weeks.

Yesterday it heard how Purdon was introduced to blue magic supplier the late Robert Asquith by the late John Seaton.

Seaton, a multimillionaire racehorse owner, was found dead at his Canterbury home in November just hours after he told Herald racing editor Michael Guerin he would fight "to the absolute limit" to clear his name and that of Purdon, who was his trainer.

Mr Asquith, 47, died a year ago at his home in North Canterbury two days before he was to appear in court. He had been charged under the Medicines Act with supplying the banned performance-enhancing substance propantheline bromide, found in "blue magic".

Both deaths have been referred to the Christchurch coroner.

The judiciary heard that Asquith had told Purdon he had an "enzyme" which might help a suspected internal bleeder such as Light And Sound. He assured Purdon it would not return a positive swab.

Purdon claimed to have no background knowledge of "blue magic" and did not know what was in the phials. He said there could be a problem after Australian trainer Rod Weightman was found to have 60 phials of a blue substance in Victoria.

Asquith reassured Purdon "he should be all right".

When police arrived it set off huge alarm bells with Purdon.

Purdon then found himself caught up in a transtasman international racing doping investigation which has haunted him for 14 months.

Penalties vary. Purdon could be fined up to $25,000, be suspended or disqualified from holding a licence for up to life.

HRNZ lawyer Chris Lange sought a year-long disqualification as a starting point.

Purdon's lawyer, Nick Davidson, QC, in summary, did not believe Purdon should be disqualified for an "innocent act".

- NZPA, staff reporter