"I understand that Mr Pora has now chosen to pursue the appeal to the Privy Council and an application for leave to appeal will be filed shortly,'' Ms Collins said.
"It would be constitutionally unsound for the Government to be considering Mr Pora's convictions at the same time through the Royal prerogative of mercy. That, and the need for a thorough examination of all evidence relied on by the applicant, is why the Government cannot immediately issue a pardon to Mr Pora.
In his opinion piece, Mr Williams said Ms Collins had previously cited the case of Arthur Allan Thomas.
"When Thomas received his free pardon from the Governor-General he had not exhausted his appeal rights, in particular, he had not conducted a substantive appeal to the Privy Council,'' Mr Williams said.
Last night, Ms Collins said that in Mr Thomas's case, a pardon was granted only after he had used his appeal rights and his right to apply for the Royal prerogative of mercy.
"Mr Thomas was granted a pardon after a thorough examination by Robert Adams-Smith QC of the evidence. This followed the Privy Council declining leave to hear Mr Thomas' appeal,'' she said.
There is a growing belief that Pora, who has spent the past 20 years in prison, could be innocent, and more people are adding their voices to calls for his release.
Last week Ms Collins admitted he may have been wrongly convicted over the 1992 murder of Auckland woman Susan Burdett.
Act leader John Banks, who was Police Minister at the time Pora was charged, the Police Association, the Maori Party, Labour and NZ First leader Winston Peters have also questioned the 1994 conviction.
Pora was convicted of Ms Burdett's rape and murder in 1994 and was again found guilty at a retrial in 2000. This was ordered after the semen in Burdett's body was found to belong to Malcolm Rewa.
Rewa was eventually convicted of Burdett's rape, but two juries couldn't decide about murder.
