The new Garda commissioner of the country will not be able to be independent after his role in his PSNI, according to the High Court.
Legal proceedings have begun in a challenge against PSNI. Deputy Chief Commissioner Drew Harris is appointed as a commissioner.
Ciaran MacAirt, whose grandmother Kathleen Irvine was killed during the Troubles, brought the action in an attempt to prevent Mr Harris from being appointed in the role.
Mrs. Irvine was one of 15 people killed by loyalists when bombing McGurk's Bar in Belfast in 1971.
After yesterday's talks, MacAirt said it was his right as an Irish citizen to point out flaws in an appointment.
"I have great fears for the basic human rights of Irish citizens when Harris is in charge of An Garda Síochána, because of what he has done over the last 15 years with regard to victims and survivors of the Troubles," he said.
Attorney for Mr. MacAirt, Gerard Humphries SC, said there was a clear conflict of interest in Mr. Harris who took the role because he was bound by the official secrecy law in Britain through his work for the RUC, later PSNI, and his role in the Historical Inquiries Committee.
They also say that the conflict is incompatible with the tasks of section 5 of the Garda Síochána law, in particular with regard to the security of the state and the investigation of crime.
"Drew Harris can not independently meet the requirements of An Garda Síochána due to his involvement in British state security and the Official Secrets Act.
"Any information he might have received on the basis of his position in the PSNI prevents him from fulfilling his duties in this role."
MacAirt, assisted by Kinnear and Co-solicitors with the help of MacGeehin Toale Solicitors in Dublin, has requested permission for a judicial review of the appointment of Mr. Harris.
The PSNI deputy is the first Garda commissioner appointed from outside the Republic and will take up the role on 3 September.
Mr Harris is a former Royal Ulster Constabulary (RUC) officer and his officer-father Alwyn was killed in 1989 by an IRA bomb.
The McGurk's Bar bombing was one of the worst atrocities of the Troubles and the families of those who died have long campaigned for a new question.
The legal challenge is countered by the state and An Garda Síochána, whose legal team is led by Remy Farrell SC.
"My argument is simply that the application is not readable and is no more than a personal opinion on behalf of the applicant.
"There has been no attempt to tackle the judicial review request, this is nothing more than a series of personal views dressed up as something else.
"An applicant does not have the right to go to court to say:" The government has made the wrong decision and I want my opinion on the issue to come in the place of the opinion of people in charge of legislative decisions " . "
Justice Denis McDonald says he hopes to take a court decision today.