Trainer John McNair has been fined $15,000 over a positive swab to methylamphetamine returned by one of his horses but stewards have acknowledged he was not responsible for giving Normandy the drug commonly known as ice.

Following an initial inquiry into the matter, stewards investigated an anonymous phone call made to Racing NSW on the morning of a Newcastle race meeting telling them McNair's horses had been illegally treated.

Among the phone records looked into was the number of a person McNair believed might have reason to discredit him.

While stewards were unable to identify the anonymous caller they were satisfied on the weight of other evidence, including a lack of abnormal betting on Normandy's race, that McNair did not treat the horse.

The trainer told stewards on the morning of March 18 his horses had not been treated and he was confident they were going to the races drug-free.

However, as the horse's trainer McNair is ultimately responsibility for presenting Normandy to race with a prohibited substance in his system.

Evidence from Racing NSW senior official veterinarian, Dr Craig Suann and Australian Racing Forensic Laboratory Science Manager, Dr Adam Cawley indicated the administration of methylamphetamine most likely took place between five to 24 hours before the race.

Dr Cawley said the amount of the drug was not consistent with human-to-horse contamination.

In arriving at the penalty, stewards took into account McNair's guilty plea and co-operation with the investigation and the consequences a disqualification or suspension would have on his stable.

But they also said his stable security was inadequate.