The Solicitor-General says the investigation of all Crown lawyers involved in a significant miscarriage of justice is about ensuring public confidence.
The Supreme Court last month quashed Alan Hall's murder conviction saying the mistakes were either incompetence or a deliberate, wrongful strategy to secure a guilty verdict.
The Crown conceded Hall's 1986 trial was profoundly unfair and constituted a miscarriage of justice.
The spotlight was now turning on the police and lawyers who helped put him behind bars.
The Solicitor-General this afternoon released the terms of reference of its investigation.
The terms of reference
Nicolette Levy QC's investigation would cover all Crown lawyers' involvement in prosecuting the case - from 1985 until 2022.
It would cover both what lawyers did and did not do, which contributed to the miscarriage of justice or a delayed resolution.
The inquiry may also identify any lessons for Crown lawyers from Hall's case, and whether further action was needed.
The Solicitor-General was yet to decide whether the subsequent report, or a summary of it, would be released to the Hall or Easton families, or the public.
It would be finished in four months, and by 9 December at the latest.
Levy "may engage" with police and the Ministry of Justice during the investigation.
Solicitor-General Una Jagose QC said the inquiry was primarily about getting the facts.
"So that, as Solicitor-General, I have a good understanding of the precise role played by relevant Crown lawyers in this matter."
Levy's report was "important for ensuring public confidence in the inquiry", she said.
Read the full terms of reference here
Podcaster's info to Crown to play a role
Some of things covered by the terms of reference included how crucial witness statements and other disclosures were not given to the defence team, and were never heard during the trial.
Important material about the case, establishing the basis for a miscarriage, was disclosed to Hall in 1988 under the Official Information Act after his unsuccessful appeal. The inquiry would look into what knowledge any Crown lawyers had about it.
It will also look at how lawyers handled information given to Crown Law in 2018 and 2020 by Newshub journalist Mike Wesley Smith - who made a podcast about the case.
The terms of reference state it was critically important that public confidence in the integrity and impartiality of the prosecution process was maintained.
The limits of the Solicitor-General's power meant Levy's inquiry would not cover Hall's three Royal Prerogative of Mercy applications.
That process was overseen by the Governor-General.
However, the actions of any Crown lawyers involved in those proceedings would be covered.
Wait continues on next steps by police
Meanwhile the police were still considering whether they would release the terms of reference of an internal inquiry into its handling of Hall's case.
The Independent Police Conduct Authority had lodged a query with the police about whether to step in, but so far the police had not responded.
Law professor Andrew Geddis said he would like to see the IPCA involved.