A trackwork rider's claim his methamphetamine use was a "one-off" was quickly dismissed by authorities because he had used the same excuse a year before.

Robert Harris, 41, a regular trackwork rider at Palmerston North's Awapuni Racecourse, was charged with breaching New Zealand Thoroughbred Racing's Rules of Racing when a urine sample taken on June 15 showed the Class A drug in his system.

Harris, who held a Trackwork Licence, was one of nine people performing a "safety sensitive activity" and randomly selected for drug testing on the day.

A recently released Racing Integrity Board decision revealed Harris had only just returned from serving an 11-month disqualification imposed in June last year, which was also for methamphetamine use, and tried to avoid taking the test by leaving the racecourse.

"The investigator drove to Mr Harris' residence and advised him that his failure to attend for testing was a breach of the Rules of Racing," the RIB's decision outlined.

"Mr Harris then admitted that he had consumed the drug methamphetamine the previous day and that he knew he would likely have returned a positive result."

Harris returned to the drug testing van and the sample he supplied was found to contain amphetamine and methamphetamine when analysed by the Institute of Environmental Science and Research (ESR).

A licenceholder breaching the rule could face a disqualification for a period not exceeding five years and/or suspended from holding or obtaining a licence for up to 12 months and/or a fine of more than $50,000.

Harris' Trackwork Licence was suspended on June 30, pending the RIB Adjudicative Committee's decision.

His previous 11-month suspension was imposed on June 25, 2021, after he test positive for methamphetamine. The disqualification was suspended for three months to enable Harris to complete a drug rehabilitation course.

The RIB investigator this time argued a suspension of 18 months was required.

At first Harris told the committee that he had only "fallen short once", by taking methamphetamine he said was offered by a friend.

His claim didn't fly with the committee, however, as it mirrored the excuse he gave to the Judicial Committee in 2021 when he then said the breach was a "one-off".

"We reject as implausible any claim that this later offence, one month after his previous term of disqualification expired, was isolated.

"Whatever counselling he has undertaken, is not achieving the desired results."

The committee adopted a starting point of a 15-month suspension but made a three-month uplift for aggravating factors, including the breach occurring a month after Harris' previous disqualification expired, he was well aware of the consequences and he tried to evade the testing procedure.

Harris was suspended for 18 months beginning on June 30.

"We do not accept that this was "one-off" offending. It has a hollow ring," the committee said.

- Leighton Keith, Open Justice