The father of the Kahui twins is seeking a judicial review of the coroner's findings on the babies' deaths.
The three-month old twin boys, Chris and Cru, died of head injuries five years ago.
The father, Chris Kahui, was found not guilty of their deaths and no one else has been charged.
The findings of Coroner Garry Evans are due to be released any day.
However, at the High Court in Auckland on Wednesday, Mr Kahui's lawyer Lorraine Smith applied for a judicial review of those findings.
She would not comment on why she has taken this action.
The legal system provides for parties to respond to a coroner's findings before they are released if they contain criticism.