Two guards were suspended from Casuarina Prison after allowing notorious jailed bikie Troy Mercanti close to a security room where weapons and tools were readily available.
Mercanti was able to stop and talk to a prison officer named Hogan in the room, who later testified he feared the Finks member would attack him because he had been repeatedly threatened by Mercanti and other bikies.
Details of the astonishing lapse of security at WA's highest security prison have emerged in a decision published by WA Industrial Relations Commissioner Stephen Kenner this week.
Mr Kenner said prison officer Daniel Ratten was subject to a serious charge of negligence and carelessness in performing his duties when escorting a violent offender such as Mercanti. "SO (senior officer) Hogan was clearly left in the position of substantial risk, to both himself and other prison officers, through the negligence of officer Ratten," he said.
The incident unfolded when officer Ratten and another officer, Phillip Clark, were taking Mercanti - who is in jail for assaulting his former partner - to punishment cells, or the "multipurpose unit" as it is formally known.
Mercanti was supposed to be escorted with one officer behind him at all times and another to the side or in front of him, the decision document revealed. A senior officer gave evidence the officers were "ahead of Mercanti and quite distant to him, to the point where he could not have been restrained if he had decided to attack senior officer Hogan".
This was disputed by the two officers. A disciplinary inquiry at Casuarina in December 2012, 10 months after the incident, led to officer Ratten and officer Clark being suspended from duty without pay and other entitlements for six days.
Officer Ratten appealed but the Prison Officers Appeal Tribunal did not uphold it.
Corrective Services Minister Joe Francis intended to transfer officer Ratten to Hakea Prison, saying he has a lack of confidence in the guard's ability to work in a maximum-security prison.
"The minister emphasised that the prisoner escort concerned involved a notoriously violent offender, and the dereliction of duty by officer Ratten exposed SO Hogan to a significant and unacceptable risk," the decision said.
The WA Prison Officers Union took officer Ratten's case to the WAIRC, arguing the minister's proposed forced transfer was "harsh, oppressive and unfair".
Mr Kenner ordered the transfer to go ahead.