Three South Australian greyhound trainers hit with life bans and big fines in the state's first confirmed case of live baiting will not face criminal prosecution.
The RSPCA says it has received legal advice that covertly taken video footage of the incident would not be admissible in court.
The footage shows two men using live rabbits as lures to train greyhounds.
It led to Greyhound Racing SA recently imposing life bans on Troy Murray, Jackson Murray and Connor Murray after the case against them was heard by its Integrity Hearings Panel.
Troy Murray was also fined $80,000, Jackson Murray $40,000 and Connor Murray $60,000 after the authority successfully applied to the Supreme Court to use the video in its internal disciplinary proceedings.
The RSPCA said its legal advice raised concerns over the video being obtained unlawfully and its provenance was unknown.
It said repeated attempts to obtain the cooperation of the person who took the video had proved unsuccessful.
"Should further evidence come to light in relation to this case that is deemed legally admissible and sufficient to support a criminal prosecution, RSPCA SA will not hesitate to proceed," the organisation said in a statement.
The latest development in the live baiting case came after the state government recently launched an independent inquiry into greyhound racing following the release of a video of a different trainer kicking and punching a dog.
Former Victorian police chief Graham Ashton will conduct the investigation that could strip the industry of its freedom to largely self-regulate.
Premier Peter Malinauskas said the conduct in the video was unacceptable and animal welfare should be a paramount consideration for the industry.
"We’ve long been assured that instances like this do not happen in the greyhound racing industry," he said.
"But in light of the available evidence, we’re not prepared to take those assurances at face value."
The RSPCA's head of animal welfare Andrea Lewis said the organisation was preparing a submission to Mr Ashton's inquiry.
“The loud and clear message from what has occurred here and in other states is that self-regulation of greyhound racing does not work,” Ms Lewis said.
“There needs to be formal and complete separation of the integrity and regulatory functions from the commercial functions."