Trainer Luke Comer has been given a three-year suspension by the Irish Horse Racing Regulatory Board and hit with costs of €755,754 after 12 of his horses were found to have failed drug tests.
The suspension is due to take effect from 1 January 2024.
Comer has also been fined €85,000 in what is one of the biggest doping scandals ever to hit the sport.
The case relates to horses He Knows No Fear, Old Tom Higgins, Boxing Hero, Grand D'espagne, Aircraft Carrier, Powerful Don, Wee Jim, Great Moon, Our Man Flint, Questionare, Green Force and Blyton which all failed tests for an anabolic steroid.
The referrals committee did not find direct evidence of deliberate doping, but found Comer responsible for serious rule breaches in the absence of any other plausible explanation for the adverse findings.
Comer admitted that traces of prohibited substances were found to be present in the horses, but he categorically denies that either he or any of his staff were involved in doping the animals.
Comer was also found to have broken a rule which states he must train horses at one stated location.
He Knows No Fear failed a drug test following a race in Leopardstown on 16 October 2021, with the same horse and the 11 others stated tested in an unannounced inspection on 10 November 2021.

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