Sydney trainer Con Karakatsanis has told a hearing it would be "madness" to administer a saline drench to a horse a few hours before it raced.

Karakatsanis and his father Tony are charged over the discovery of stomach tubing equipment including a saline and electrolyte mixture belonging to them during a raid by stewards on the stable housing their horse Howmuchdoyouloveme hours before it ran at Flemington on Derby Day last year.

Karakatsanis admitted during Monday's inquiry before the Racing Appeals and Disciplinary (RAD) Board in Melbourne, Howmuchdoyouloveme was a horse that dehydrated badly and regularly required drenching.

But in response to questioning by his counsel James Tobin, he said the horse never received the treatment on the day it was due to race.

"You would be absolutely crazy to give a saline drench three hours before a race," Karakatsanis said.

"It would be madness."

The RAD Board has heard no evidence that Howmuchdoyouloveme received any treatment, merely that Karakatsanis and his father, who is a registered stablehand, "connived or conspired" to administer a treatment within a time period precluded by the rules of racing.

They face a combined total of five charges to which they have pleaded not guilty.

The hearing also heard allegations that one of the two stewards involved in the raid approached the situation with a pre-conceived notion that the father and son team was "up to no good".

Steward Kane Ashby told the RAD Board he had covertly observed Con Karakatsanis, his father and two other men in the stable complex.

He told the Board he heard Karakatsanis talk about "looking after the gate" to the stables and saying he would phone his father if any problems arose.

Karakatsanis' counsel suggested Ashby hadn't heard the words he testified to in their full context and had applied his own interpretation to them based on a view that something improper was going to happen.

"That view shaped your whole outlook," Tobin told Ashby.

"You have drawn inferences at every step that were adverse.

"You brought a suspicious mind to the stable."

Ashby rejected the suggestion, saying he observed Con Karakatsanis acting suspiciously before the tubing equipment was discovered.

The Board heard Ashby and fellow steward Dion Villela had gone to the stable after being tipped off that Howmuchdoyouloveme was to be tubed within the prohibited period before it ran.

But Tobin said the pair had only a 10 minute time frame in which to perform the alleged procedure, a period that would have been insufficient for the task.

Tony Karakatsanis has admitted placing the bag containing the tubing equipment in the horse's box, but said he did so in the mistaken belief the bag contained hay.

He said the tubing gear had been on the premises so Howmuchdoyouloveme could be treated after it raced.

After a raceday inquiry, the horse was allowed to take part in the Group Two Yellowglen Stakes in which he finished eighth as the $3.10 favourite.

The inquiry continues on Tuesday.