[citation needed] O'Shaughnessy carried out his practice on the Connaught and North Eastern Circuit.
He served as counsel to the plaintiffs in relation to the disastrous rail accident during a school outing from Armagh to Newry.
O'Shaughnessy won a great reputation from this trial, and took silk (an informal term for Queen's Counsel) soon after.
[1] Maurice Healy remarked that there was a rather unfriendly rivalry between himself and William Huston Dodd as to which of them was entitled to be called "Leader of the Bar".
The Recordership was abolished in 1924 and O'Shaughnessy became a judge in the High Court of the Irish Free State.