The Department of Corrections is still to use a new law designed to protect the public from high-risk offenders.
Public Protection Orders (PPOs) came into law in December 2014 and allow high-risk criminals to live on prison grounds rather than in the community after they complete their sentence. Corrections has applied for a PPO three times. None has been granted.
Acting deputy national commissioner Darius Fagan acknowledged how difficult it was to get a PPO enforced.
"Only a very small number of people are likely to become subject to public protection orders, and the threshold is very high."
Labour's Corrections spokesman, Kelvin Davis, said if the legislation couldn't be used on a high-risk rapist, as in the latest case, it was time the law was reviewed.