O'Doherty joined the IRA in 1958 in his native Carrick-on-Suir, County Tipperary, and participated in the Border Campaign.
He remained in this position until his own arrest and imprisonment in Portlaoise Prison in 1974.
He subsequently undertook a number of missions in various parts of the world on behalf of the IRA.
In the 1986 split in the republican movement, O'Doherty sided with Republican Sinn Féin and refused to recognise the legitimacy of Dáil Éireann in Leinster House.
O'Doherty felt that the decision to recognise the Republic of Ireland was a "greater treachery even than Collins and company".