Father-and-son racehorse trainers Lee and Shannon Hope want three urine samples to be re-examined with a high-tech new testing method as they fight lengthy bans for administering cobalt.
Lee Hope was disqualified for three years and his son Shannon for five in November 2015 when they were found guilty of dosing three horses with cobalt to affect their performance.
But they launched an appeal against the bans in the Victorian Civil and Administrative Tribunal and they continue to train under a stay of proceedings until their case is heard.
The VCAT hearing began on Tuesday with the Hopes making an application to re-test urine samples for each horse.
They are seeking to use a new testing technique that can identify the proportion of "organic" and "inorganic" cobalt in the urine.
Their lawyer Rahmin de Kretser argued cobalt is found in organic feed and vitamin B12, which are routinely given to horses and not deemed to be performance-enhancing.
Mr de Kretser said this new test could show that the cobalt in the urine may have been predominantly "organic", coming from these cobalt-containing products.
"It would be relevant to penalty," he said on Tuesday.
"It would mean the cobalt administered was not performance enhancing.
"But it also goes to their belief of whether what they did was honest and reasonable."
Mr de Kretser also mentioned a "bio-accumulation" affect that may have occurred while giving the horses cobalt-containing feed, giving rise to the levels.
He said the tests should be done in the interests of fairness, and added there was a chance the results could actually go against the Hopes.
Racing Victoria, which controls the samples, opposed the re-testing application.
Expert witness Dr John Vine, a scientific consultant, said the new test is not yet accredited for horse racing.
"It would be purely done as a piece of research," Dr Vine told the tribunal.
But Mr de Kretser said there were labs in Australia willing to perform the test, which would be for the purposes of the tribunal appeal hearing.
The Hopes were subject to the first cobalt inquiry in Victorian thoroughbred racing.
Their case was viewed as a test of whether the race-day threshold of 200 micrograms per litre was enforceable.
The national rule came into effect in January 2015 but it has since been halved to 100mcg/L.
The hearing continues before Justice Greg Garde on Wednesday.