The stablehand at the centre of the 'Aquanita eight' doping conspiracy will give evidence as four trainers fight their disqualifications.

Float driver Greg Nelligan has been subpoenaed to front the appeal hearing over Australia's biggest racing scandal on Monday.

Nelligan, like trainer Robert Smerdon, was a key player in the top-ups scheme, Racing Victoria barrister Jeff Gleeson QC told the Victorian Civil and Administrative Tribunal last week.

Nelligan and Smerdon were both disqualified for life by the Racing Appeals and Disciplinary Board, which described them as the driving forces behind the systematic conspiracy to cheat in more than 100 races over seven years.

It said Nelligan, while further down the chain of command, was the architect and to some extent the promoter of the scheme to give horses top-ups of sodium bicarbonate and Tripart paste on race days.

The stewards' case relied on 1000 text messages found on Nelligan's mobile after he was caught inserting a syringe into the Smerdon-trained Lovani's mouth on Turnbull Stakes day in October 2017.

Nelligan's wife Denise ultimately blew the whistle on the whole saga when she confessed to the contents of the top-ups in an interview with stewards, the RAD Board noted, rejecting her later attempt to renege.

Eight people associated with thoroughbred management company Aquanita Racing were disqualified over the illegal race day treatments.

Trainers Smerdon, Stuart Webb (banned for four years), Tony Vasil (three years) and Liam Birchley (one year) are fighting their disqualifications.

The Nelligans are due to appear at VCAT on Monday.

Trainer Trent Pennuto and stablehand Daniel Garland, who were disqualified for two years and one year respectively, denied being involved when they gave evidence last week after being subpoenaed by RV.