Leading trainer Chris Waller has been fined $30,000 for presenting a horse to race with the prohibited substance methylamphetamine its system.

Like Waller, Racing NSW stewards said they could not determine how the illicit substance, commonly known as ice, came to be in the horse’s system when he raced at Canterbury on October 5.

Other known cases have come from cross-contamination from human-to-horse contact.

Stewards were, however, critical on Friday of security measures in Sydney’s largest stable and concerned that random testing of staff had resulted in positive results to banned substances.

They were satisfied that the one person who returned a positive to methylamphetamine would not have been near Betcha Thinking but concerned about five positive tests to other drugs and alcohol.

A glitch in the CCTV recordings meant some data could not be stored so not all movement in the stables was captured.

Waller has since introduced workplace testing of his staff having previously relied just on random testing of stablehands conducted by Racing NSW.

Betcha Thinking has been stripped of his second placing in the race at Canterbury.