Cusack-Smith was called to the Irish Bar in 1788, having studied at Lincoln's Inn, became King's Counsel in 1795, and was made Solicitor-General for Ireland in 1800.

O'Connell raised a motion, carried by MPs on 13 February 1834, to appoint a select committee to enquire into the conduct of Lord Smith in respect of his neglect of duty as a judge, and the introduction of political topics in his charges to grand juries.

On the count of neglect, Cusack-Smith had been accused of rarely beginning his court sessions until after noon, occasionally running them until late into the night.

[1]The accusation of introducing political topics stemmed from statements made from the bench to grand juries condemning partisan agitation practices, which were themselves perceived as inflammatory due to their one-sided nature, although in fairness he was far from being the only judge to behave in this manner.

Despite this reversal, his conscientious conduct as a judge was well thought of to the extent that he was even congratulated by voices among the Repealers movement on his escape from parliamentary inquiry.