A stablehand mistakenly gave a racehorse large doses of a hoof treatment and trainer Peter Moody knew nothing about it, a cobalt inquiry has heard.

Moody's legal counsel says the trainer is not guilty of intentionally administering cobalt to affect Lidari's performance in the 2014 Turnbull Stakes, a charge carrying a minimum three-year disqualification.

Barrister Matthew Stirling has told a tribunal Lidari was given Availa, an oral treatment to help horses with shelly or cracked hooves, that contained cobalt.

But Racing Victoria stewards' barrister Jeff Gleeson QC told the Racing Appeals and Disciplinary Board not to believe the "hopeless" belated story.

"It defies belief that Mr Moody's stable would, for months on end, administer a hoof powder at seven times the quantity recommended by the manufacturer," Mr Gleeson said.

"We say that you'll find that the belated story is hopeless and transparently does not explain the amount of Availa that Lidari was receiving in October 2014."

Mr Stirling said the Moody camp accepted an assistant stablehand, Rami Myala, made a mistake by giving Lidari seven times the recommended quantity of Availa.

"Mr Moody certainly didn't give the instruction. Mr Moody didn't know that Mr Myala was giving such a large dose of Availa," Mr Stirling said.

"This is a case of a simple mistake which occurs in racing stables from time to time.

"Their stable staff are carrying out menial tasks across dozens and dozens of horses and a mistake is made."

Mr Stirling said there was no evidence connecting Moody to cobalt and the case was hollow.

Mr Gleeson said the tribunal should reject the argument Moody did not know what Mr Myala was doing in relation to one of the most significant matters in his career as a trainer.

"It seems in what can only be described as a somewhat desperate measure that Mr Moody is attempting to embrace negligence as an excuse for the elevated cobalt reading," Mr Gleeson said.

"It seems that what he's saying is my stables for months give hoof powder seven times above the manufacturers' recommended dosage and I had no way of knowing."

Moody has pleaded not guilty to three charges after Lidari returned levels of 380mcg per litre of urine and 410mcg, well above the legal threshold of 200mcg.

But Mr Stirling says Moody will plead guilty to presentation, and not administration, if the defence successfully argues to have some of the testing certificates excluded.