O'Callaghan was first elected to the Dáil in the 2016 general election. He has worked as a law lecturer, barrister and senior counsel. He is the party spokesperson on justice and equality. He played senior rugby for Leinster and Connacht.

I have a strong voice for criminal justice reform. My Parole Act will keep serious offenders in prison for longer than before.

To oppose the proposed environmental destruction contained within plans such as Bus Connects and replace them with a metro system for Dublin.

To enact a comprehensive criminal justice agenda which will toughen laws against domestic violence, knife crime and gender-based violence against women. I also want to tackle the housing crisis.