The Hon. William J. O’Brien is an acting justice for the Nassau County Supreme Court in the Tenth Judicial District of New York. He was initially elected to the Nassau County District Court in 2001. Then, in 2015, he was elected to the Nassau County Court.
O’Brien earned a B.A. from Fordham University in 1978. He then completed a J.D. from St. John’s University School of Law in 1981.
He began his legal career as an associate at Sandback & Birnbaum in 1982. He practiced there for two years, eventually leaving to become a law clerk at the Nassau County Court. He served in that capacity until 1997, when he joined the New York State Unified Court System as a Nassau County Courts Administrator.
O’Brien has served as president of the New York State District Court Judges Association. He has also taught as an adjunct professor at Hofstra University and Long Island University.
He is registered as a Republican.