The Spirit of Tasmania ferry operator has had a small victory in its legal fight over the deaths of 16 polo ponies.
The horses had competed in a tournament and were travelling from Devonport in Tasmania to Melbourne in a converted refrigeration trailer on the night of January 28, 2018.
They were discovered dead when the trailer was opened at Yarra Glen in regional Victoria about 7.15am the next day.
Two horses, named Scarlet and Delilah, survived.
Magistrate Leanne Topfer ruled the company failed to inspect the trailer to ensure the horses were correctly individually stalled and to ensure ventilation was adequate.
Ferry operator TT-Line launched an appeal in the Supreme Court of Tasmania, arguing its conviction for using a method of management likely to result in the animals' unjustified pain and suffering should be quashed.
The Supreme Court on Monday ruled the guilty verdict for the charge should be set aside, and the matter should be re-heard by a different magistrate.
The ferry operator did not seek a review of its other 28 convictions for breaching the animal welfare act.
It was fined a total $75,000 last year.
Justice Stephen Estcourt found the magistrate erred in law, including by failing to properly consider whether the ferry operator took all reasonable measures to ensure the horses' welfare.
"In my view, in failing to consider what measures might have been taken by the applicant in order to prevent the pain and suffering to the horses and then considering whether such measures were reasonable measures in all of the circumstances, Her Honour erred in law," Justice Estcourt said.
The magistrate also failed to properly consider whether the ferry operator made an honest and reasonable mistake when it relied on the declaration of the experienced trailer driver, the judge said.
The driver owned the horse trailer for many years and had previously completed nine uneventful trips on the Spirit of Tasmania during summer.
Acting Justice Brian Martin said the conviction should be set aside and ferry operator should be found not guilty of the charge.
The magistrate erred in finding the ferry operator's failure to ensure the horses were individually stalled caused a "prohibited risk", he said.
"As the failure to individually stall the horses did not possess any causative effect, a failure to inspect to ensure individual stalling could not contribute to the method of management being reasonably likely to bring about the prohibited result," Acting Justice Martin said.
Acting Justice David Porter agreed the matter should be re-heard by a different magistrate.
