High-profile Victorian jockey Danny Nikolic says he'll take a lie-detector test in a bid to prove he didn't speak about the prospects of a horse trained by his brother.

Nikolic told the Racing Appeals and Disciplinary Board on Tuesday he had not discussed the chances of Baby Boom, trained by his brother John, with disqualified bookmaker Neville Clements before it raced and was defeated at the Gold Coast on January 3, reported the Herald Sun.

Clements laid Baby Boom to lose on Betfair - which allows such transactions - and won $56,040 when the horse finished fourth.

"Let me be very blunt ... I reckon before Baby Boom raced that you spoke to Neville Clements about the horse," said Paul Holdenson, QC, appearing for Racing Victoria stewards. Nikolic replied: "I would love to take a polygraph test. I never spoke about the horse. You're 100 per cent wrong."

Holdenson took Nikolic through each of the nine horses he had ridden that Clements had laid to lose on Betfair and asked him if he had discussed the "prospects or lack of them" with Clements.

Nikolic, facing four potentially career-threatening counts of improper practice and acting in a manner prejudicial to racing, said he spoke to Clements before most meetings, as he did with another form analyst, Mark Hunter, but the talk was about the speed and tempo of races.

At the core of the Nikolic case is the nature of racing relationships.

The stewards asked the appeals board, before Judge Lewis, to join dots and conclude that the relationship between Nikolic, Clements and one or two others teetered between inappropriate and corrupt.

The two pivotal dots - that Nikolic had "hooked" (pulled up) horses Clements had backed to lose - could not be joined because Nikolic has not been charged with any riding offence.

An attempt by chief steward Terry Bailey to suggest some rides were "questionable", despite a lack of relevant charges, was ruled inadmissible, as was a DVD Bailey brought to the room, featuring these "questionable" rides. Stewards brought next to nothing to the table, bar a DVD that remained in its plastic cover.

They proved that Nikolic had phoned Clements - and, occasionally, Nikolic's brother John, who then spoke to two of his mates, who then had some bets - at around the time that Clements had laid some Nikolic mounts on Betfair.

On face value, this is interesting, especially in the era of Betfair, which allows horses to be backed to lose, and especially given Clements' betting records proved the only time he bet big time on horses to lose was when Nikolic was riding them.

Counsel for the stewards produced example after example of beaten Nikolic rides that Clements had plonked to lose in the hope that they could successfully mount a circumstantial case - a joining of dots - if they produced enough phone-call-to-winning-bet patterns.

The Racing Appeals and Disciplinary Board was asked to join more dots when an odds-on favourite trained by Nikolic's brother was beaten at the Sunshine Coast.

The stewards questioned why Nikolic had spoken to his brother, who spoke to two punters, who backed the odds-on favourite to lose - it ran fourth - and why Clements got into the act after John spoke to Danny, who spoke to Clements.

Nikolic's counsel, Richard Smith, said there was no evidence Nikolic had discussed his rides with Clements but offered: "What if he did?"

Nikolic and Clements have been mates for 20 years. They talk about lots of things and Smith said there was no rule that could prevent Nikolic talking about his rides to Clements; that jockeys, bookies and punters talked; that it was part of life at the racetrack.

While Judge Lewis speculated there must be a line in the sand where such relationships and conversations might be inappropriate, it seems there is no rule to define it.