A legal expert says the Justice Minister's call to refer the Scott Watson case to the Court of Appeal is the right move.
But victims' advocates are concerned the wounds will be reopened for the families of his alleged victims.
Watson, who turns 49 on Sunday, was convicted of the murders of Ben Smart and Olivia Hope in 1999. Their bodies were never found.
Watson has always denied killing the pair, who were last seen getting off a water taxi and onto a boat early on January 1, 1998.
After a former High Court Judge reviewed Watson's application for the royal prerogative of mercy, Justice Minister Andrew Little advised Governor-General Dame Patsy Reddy to refer the convictions to the Court of Appeal for further consideration.
"It's not without controversy, this case, but I believe that is the right decision - for it to be referred back to the Court of Appeal," Massey University legal expert Chris Gallavin told Newshub.
"I don't believe there is enough evidence for us to reliably say that beyond reasonable doubt, those charges have been proved against him... I just don't believe there's enough evidence there for us to hand-on-heart say this is a sound and safe conviction."
The Sensible Sentencing Trust has asked Little to ensure Smart and Hope's families are well-supported as the case is thrust into the spotlight again.
"Every time an appeal is made, it just brings everything back - it brings it right back from the day the crime was committed," said spokesperson Jess McVicar.
"Please ensure that some support is put in for the Smart and Hope families because it is going to be a very traumatic time... They're having to go through a lot of pain, a lot of trauma, a lot of emotion. It's horrible."
Watson has been denied parole every time he's applied.
In a 2015 interview with North & South, Watson claimed police planted evidence in his boat - two pieces of hair.
"Nothing Scott Watson has said to me during our interviews has made me feel any better about the fact he is in prison - if anything it's confirmed my doubts and unease about the conviction," journalist Mike White, who interviewed Watson, said.
DNA testing has come a long way since 1999.
"The microscopic comparison of hair is no longer regarded as a very strong or high quality part of evidence. Because of that it would be strongly challenged today, if it was presented in court," a report by forensic consultant Sean Doyle said, RNZ reported on Friday.
"Again, the DNA analysis back in those days wasn't as sophisticated or as discriminatory as it is today and therefore that DNA evidence would be more strongly challenged if it was presented in court today."
The team that helped free Teina Pora in 2017 turned its attention to Watson's case. It's expected to be the final case eligible for a royal prerogative of mercy, with the new Criminal Cases Review Commission coming into force from July.
Watson's legal team are expected to apply for bail now the case is back in court.