The Queensland Racing Integrity Commission has discontinued proceedings against trainers Ricky Vale and Tony Gollan on positive swab charges because of procedural issues.
The decision means Rockhampton-based Vale, who was disqualified for a year, can return to training.
Gollan was fined after his case was heard but he will now have the conviction struck from his record.
It is understood at least one other case is under review and lawyers for other trainers who have been convicted of positive swab charges are looking to see if they are eligible for a review.
Vale's case involved a report from the Racing Science Centre that cobalt was detected in urine samples taken from Prince Dan at Mackay in March 2016, Reset Our World at Rockhampton in March 2016 and Shepiktus at Rockhampton in March 2016.
Dexamethasone was detected in a urine sample taken from Prince Dan at Rockhampton in February 2016.
Gollan's case involved an analysts' findings that the urine sample taken from Amexed at Ipswich on June 18 last year contained Prednisone and Prednisolone.
QRIC Commissioner Ross Barnett said both the A and B samples relating to each of the positive swabs that were detected before the Commission began operations in July last year were tested at the Racing Science Centre.
He said the second sample should have been tested at another accredited facility to confirm the findings.
"This departure from normal process occurred on the basis of legal advice sought, accepted and implemented before the Commission commenced which we now accept was misinterpreted. I am aware that there may be a third case subject to a similar outcome in the coming weeks," Barnett said.
"Following submissions by legal representatives for the trainers involved, Tony Gollan and Ricky Vale, the Commission has come to a decision that the matters should be discontinued."
He said changes to testing procedures which came into effect with the implementation of the Racing Integrity Act 2016 on July 1 last year now ensured complete clarity over the correct procedures to be followed.
"All testing since that date has strictly complied with these procedures," Barnett said.
"The decision to discontinue these historical matters is not a reflection of the honesty, dedication and professionalism of the QRIC staff involved including the stewards, veterinarians and Racing Science Centre analysts.
"All staff have acted in good faith and with integrity."
