The long-running case mounted by Victorian stewards against Sydney trainer Con Karakatsanis and his father Tony had "radically altered" during its hearing and should be dismissed, the Racing Appeals and Disciplinary (RAD) Board has heard.

The two men face charges in relation to the discovery of stomach-tubing equipment in the stable of their horse Howmuchdoyouloveme hours before it raced at Flemington on November 3.

Stewards found the equipment, along with a preparation of salts used for rehydration, in a chaff bag and duly laid five charges against the Karakatsanises including one intending to stomach-tube the horse inside the prohibited, 24-hour period before a race.

But with the inquiry almost at its end after two days of evidence, lawyer Terry Tobin for the accused, said his opposing counsel, having accepted the defence case that the treatment was to be administered after the race, had come up with a new accusation that the real intention was to administer a pre-race bi-carbonate solution.

"We are being presented at the last moment with an entirely different case," Tobin told the Board.

"The charge against my clients is incoherent.

"At the end of the day we have a new case to answer."

The stewards' counsel Dr Cliff Pannam initially argued that Tony Karakatsanis had intended giving Howmuchdoyouloveme the saline drench before it raced.

He maintained that Con Karakatsanis had been designated as a lookout while the treatment was administered and had been locking the stable gate when stewards arrived.

But veterinary evidence showed that such a treatment so close to a race could seriously harm the horse, leading to Dr Pannam altering course and suggesting the alternative offence of unlawfully administering the bi-carbonate solution.

Bi-carbonate drenches are a recognised performance enhancement and their use is restricted in Australian racing.

Tobin argued that the only bi-carbonate available for the alleged tubing was located in a feed room outside the gate that the stewards maintained Con Karakatsanis was locking.

Had he succeeded in locking the gate he would have effectively cut off his alleged co-conspirators from the bi-carbonate.

Dr Pannam countered that it wasn't up to the stewards to prove the nature of any substance they found, only that the horse was to be tubed within the prohibited period.

The Board reserved its position on the application, adjourning the hearing until January 21 when both sides can present new arguments.