Three serving and one former senior police officer, including the man who is in charge of the investigation into the British army agent known as Stakeknife, are in contention for the post of PSNI chief constable, according to senior sources.
Interviews for the job of successor to George Hamilton, who is retiring at the end of next month, are to take place next week and among the four candidates who have made the short list is Jon Boutcher, chief constable of Bedfordshire police in Britain, the sources said.
Mr Boutcher is leading the inquiry into one of the British army's most senior moles within the IRA, Freddie Scappaticci, the agent known as Stakeknife.
Also in the running for the top post are the current PSNI deputy chief constable Stephen Martin, one of the force's assistant chief constables Mark Hamilton, and Simon Byrne, former chief constable of Cheshire police in Britain.
Mr Byrne was suspended from his post in 2017 after facing more than 70 separate allegations of bullying, charges that he denied. The following year he was cleared after an investigating panel found no proof of the allegations of misconduct or gross misconduct. His contract had expired by then and he was unable to resume his chief constable duties.
The interviews will be carried out by seven or eight political and independent members of the North's 19-member Policing Board under its chairwoman Anne Connolly.
A human relations officer, an occupational psychologist and an external police adviser also will have a watching brief during the interviews, although they will play no part in making the appointment.
When the board chooses a successor to Mr Hamilton, in the absence of the Northern Executive, it will be for the Northern Secretary Karen Bradley to accept or reject the recommendation.
There has been great sensitivity around the selection process after the Sinn Féin leader Mary Lou McDonald said in February no one within the senior ranks of the PSNI was capable of taking on the post of chief constable.
At the time Mr Hamilton said the comments amounted to an “extraordinary interference in an open and transparent selection process”.
Ms McDonald's remarks also prompted the Policing Board to get legal advice about how it should conduct the selection process. Sinn Féin will have one of its Assembly members, Linda Dillon, on the interview panel.
Mr Boutcher is head of Operation Kenova, which is seeking to discover how the British Army’s covert Force Research Unit (FRU) ran Stakeknife over a period of 25 years from the late 1970s to 2003 when he was exposed as an agent.
It is alleged that Stakeknife may have been implicated in up to 50 murders, particularly when he was head of the IRA’s internal security unit, its so-called “Nutting Squad” that sought to expose informers.
Mr Boutcher told The Irish Times last December that as part of his inquiry he was interviewing current and formers heads of MI5, British army generals and former PSNI and Royal Ulster Constabulary chief constables.
There are two PSNI candidates. Last July Stephen Martin was appointed as temporary deputy chief constable after the previous deputy Drew Harris was appointed as Garda Commissioner. He has served for more than 30 years in the RUC and PSNI.
Assistant chief constable Mark Hamilton has been a police officer for 25 years, also serving both in the RUC and PSNI in a wide range of posts in the Armagh and Belfast areas.