He was previously a barrister, legal academic, political adviser, and was a member of Dún Laoghaire–Rathdown County Council for the Labour Party.

[7][8] Humphreys was a lecturer at UCD and University College Cork between 1990 and 1993,[5] and also taught at the law faculties of TCD and NUI Galway.

[9] He became a legal adviser to Mervyn Taylor at the Department of Equality and Law Reform in January 1993,[13] holding that position until 1997.

[16] Humphreys was appointed to the High Court in October 2015,[17] by the Fine Gael and Labour Party coalition government.

The Supreme Court of Ireland in 2018 reversed this reasoning but upheld the order that the Minister was obliged to consider the rights that would accrue on birth of the child.

[21][22] In 2018, he ordered the State Examinations Commission to expedite its decision on an appeal to the awarding of Leaving Certificate points.