Justice Minister Judith Collins says she has taken advice from officials in response to calls to re-examine the Teina Pora case.
But the minister said on Monday it is up to his lawyers as to whether they go to the Privy Council or complete an application for a Royal prerogative of mercy.
Pora has spent 20 years in jail for the rape and murder of Susan Burdett in 1992 - crimes he says he didn't commit.
The Police Association wants Pora's conviction reviewed, saying there is sufficient concern among some senior detectives to warrant an inquiry.
Ms Collins says Pora's legal team filed an incomplete application for mercy in 2011.
She says if that option is pursued, that would involve an inquiry into Pora's conviction and possibly the appointment of an independent person such as a retired High Court judge or Queen's Counsel.
Ms Collins says the other option available is an appeal to the Privy Council.