The career of Gordon Elliott hangs in the balance with the IHRB's referrals committee hearing evidence on Friday morning after the leading Irish trainer was pictured sitting on a dead horse.
Elliott has been "cooperating fully" with the IHRB following the emergence of the photograph on social media last weekend.
The 43-year-old apologised "profoundly" for the incident.
The top Irish trainer has subsequently become subject to a temporary British Horseracing Authority ban on running any of his string in Britain, while top owners Cheveley Park Stud have moved their high-profile horses away from his yard.
- Gordon Elliott apologises 'profoundly' for photo
- BHA bars Gordon Elliott from British races
- Tiger Roll withdrawn from Grand National over weight
Racing authorities in Britain and Ireland condemned the image, which Elliott confirmed in a statement on Sunday evening was genuine.
The British Horseracing Authority said it was "appalled" by the image and banned Elliott from saddling runners in Britain while the investigation was undertaken.
While eCOMM Merchant Solutions, the company of prominent owners Noel and Valerie Moran, terminated its contract with Elliott, Gigginstown House Stud, run by Michael and Eddie O'Leary, said on Monday it would continue to support the trainer.
Many of its runners though face the prospect of being barred from the lucrative Cheltenham Festival later this month.
Among the eight Cheveley Park Stud horses currently trained by Elliott is Cheltenham Festival favourite Envoi Allen, who is moving to fellow Irish trainer Henry de Bromhead, along with stablemates Quilixios and Ballyadam.
Elliott has also won the Grand National three times, including twice with Tiger Roll. The festival at Aintree takes place on April 8-10.
BHA equine health director 'shocked'
Former trainer James Given, now the BHA's Director of Equine Health and Welfare, believes the ruling body made the correct decision in deciding to temporarily suspend Elliott from making entries in Britain.
"These are unprecedented times," Given told Sky Sports Racing.
"Gordon, at the moment, holds more entries in Britain than almost any other trainer - and so we felt it was appropriate to take the action that we have, while we wait for the Irish to complete their process."