On leaving University, Damien went to work in the Department of Justice for 2 years. On leaving the Department of Justice he lectured in the third level sector in Galway, Letterkenny and Sligo. In 1980 while working in the world of academia, he qualified as a Solicitor. He set up his own practice in Sligo in September of that year.

In the early years, he built his reputation as a tough and courageous litigator. Over the years, he has been involved in some landmark Court decisions particularly at High Court and Supreme Court levels. During the course of his career he worked almost exclusively for Plaintiffs and very often the Defendants were the State itself or State Agencies and included Local Authorities, An Bord Pleanala etc.

Damien has also excelled in the extremely complex and emotionally charged area of Medical Negligence. He has been involved in some of the largest awards in the Irish Courts made in favour of the victims of medical misadventure. His reputation in this area is evident from the fact that he attracts work from every province and often clients are referred from other firms of Solicitors.