Born in Tucson, O'Dunne was the son of Judge Edmund F. Dunne, who was Chief Justice of the Arizona Territory at the time.
He and his spouse owned a home in Baltimore and a summer residence in Blue Ridge Summit, located in Pennsylvania.
During his time spent as a judge on the Supreme Bench of Baltimore he was considered a fearless and fair leader in the judicial system.
During his forty-five years as a judge he helped clean up many aspects of the legal system including, but not limited to; fixing the penal establishment, abolishing the ancient Black Hand of the Justices of the Peace, reorganizing the state's legal business, and attacking on the old fee system.
He also was responsible for the desegregation of golf courses in the city of Baltimore; as long as the member dues were paid color was not to be a factor of who was allowed.
O'Dunne's main goal was to keep the streets safe and free of any criminal behavior regardless of its degree of offence, but would become highly irritated with those police officers that tried to wrongfully accuse a man of a crime.
Instead he shocked the public with a quote from Shakespeare's Othello, "I do perceive here a divided duty…" and continued to look at the prisoners escape as not a bad, but a good thing.
In retirement O'Dunne practiced law with one of his sons and worked as a public relations counsel for the local liquor industry.