A date is yet to be set for a hearing in the Court of Appeal.
The murderer's lawyer, Ian Brookie, told the Herald that Rachael Reed QC will advocate for the 28-year-old man at the appeal stage.
"Sometimes trial lawyers consider that it may be helpful for another lawyer to review afresh the trial and sentence process when an appeal is being considered," Brookie siad.
"That has been recommended to [my client] and has happened here, with our assistance. The appeals filed will be advanced by that lawyer for this reason."
Crown Law has been approached for comment.
The killer was last month sentenced to life in prison with a minimum period of 17 years for murdering the British backpacker.
The man, who still cannot be named for legal reasons, was convicted of murder last November for strangling Millane to death in an Auckland hotel room.
CCTV showed the pair appeared to be enjoying each others' company as they returned to his small downtown Auckland apartment.
But the university graduate would never leave the room alive - her body later found dumped in a shallow grave in the Waitākere Ranges.
After hearing from nearly 40 witnesses during the highly charged and emotional trial, the jury's decision was unanimous.
Millane's mum Gillian at last month's sentencing said her kind and intelligent daughter's dream to travel the world had turned into a nightmare that ripped the family apart.
"She died terrified and alone in a room with you ... all her dreams and aspirations taken," Gillian Millane said in a victim impact statement.
Justice Simon Moore said this was not a case where the strangulation was driven by rage or was premeditated.
But Millane was vulnerable and appeared to be restrained, he said, while the 28-year-old killer's actions in photographing her naked body after the murder were "depraved".
"You were in a position of total physical dominance," the judge told the killer last month.
"You were a stranger, she trusted you."
