The prison officer, who cannot be named, spent about four months behind bars this year, after his former partner accused him of raping and bashing her.

The woman, a former NSW police worker, had started a new relationship with a police officer, and was locked in a family court battle with her ex.

The accused man spent all of his time in the notorious Goulburn jail, locked in solitary confinement for protection from other prisoners.

He has spoken of fearing for his life behind bars, knowing he was a target for other inmates because of his job at the Alexander Maconochie Centre.

Detectives became suspicious about the woman as she continued to make allegations against her ex's family, alleging they were harassing, intimidating and committing crimes against her.

She was put under covert surveillance, and police found evidence to suggest she had been lying about her ex's family.

The woman was charged with making false accusations, and the prison officer was freed on bail in unique circumstances.

The botching of the case has sparked an internal investigation within the Australian Federal Police.

One officer is understood to have already quit.

Last month, prosecutors dropped the rape and most serious assault charges against the prison officer.

On Monday, a range of common assault charges were withdrawn in the ACT Magistrates Court.

The prosecution said it had no evidence to offer, and Magistrate Peter Dingwall ordered them to pay court costs.