After his release in 1984, his father wrote a book about his prison experience called "Inside an English Jail", which was published posthumously in 1987 under the name of Raymond McLaughlin.

He left school at the age of 14 and later returned to education as an adult through community development studies and distance learning.

His work as a community activist and political representative had led him to speak at conferences across Europe on the issues of unemployment, regional neglect and rural poverty.

He was also elected to Donegal County Council in 2004 representing the Inishowen local electoral area and was re-elected in 2009.

[7] Mac Lochlainn has been a prominent supporter of the cause of Palestinian independence and statehood and he is the Secretary of the Oireachtas Friends of Palestine group of TDs and Senators.

[8] In June 2012, the Irish Independent newspaper alleged that Mac Lochlainn and his party colleague, Deputy Pearse Doherty had "diverted unspent travel and accommodation expenses towards hiring part-time party workers despite these expenses being supposed to be returned to the Oireachtas under rules introduced in 2010".

[10][11] In December 2012, Mac Lochlainn was suspended from the Dáil after he accused the Ceann Comhairle Seán Barrett of "double standards and hypocrisy".

[14] At the 2016 general election, Mac Lochlainn ran as one of three Sinn Féin candidates in the new five-seater Donegal constituency.

Mac Lochlainn was re-elected to the Dáil at the general election of February 2020 behind Pearse Doherty, both on the first count and both exceeding the quota.