Commissioner Erin M. O'Connell-Diaz received her undergraduate degree in History and Government with honors from St. Mary's College of Notre Dame, South Bend, Indiana. She graduated from Loyola University School of Law in Chicago with a Juris Doctorate.
She was then appointed by the Illinois Attorney General to serve as an Assistant Attorney General in the General Law Division. In that capacity she represented over 150 state agencies in matters ranging from complex construction contract litigation to prisoner civil rights cases.
In 1991, she was appointed as an Administrative Law Judge for the Illinois Commerce Commission. In that role, Commissioner O'Connell-Diaz handled a full spectrum of dockets involving all aspects of utility regulation including electric, gas and water utility rate cases, consumer complaint cases, telecommunication arbitration and certification cases. In 2001, she was appointed Assistant Director of the Administrative Law Division. Additionally, she has served as Chair of the Chicago Bar Association's Public Utility Law Division.
In April 2003, she was appointed to the Illinois Commerce Commission and reappointed to a second term in 2008. She currently serves as the chairman of the ICC's Water and Transportation Committees. Commissioner O'Connell-Diaz serves as Vice-Chair of the Committee on Electricity for the National Association of Regulatory Commissioners as well as a member of its Committees on Critical Infrastructure, Water and International Relations.
Commissioner O'Connell-Diaz is married and is also active in her community serving on the board of the Bull Valley Association and Board of Trustees for Regina Dominican High School. In addition, she is a lifetime member of the Naval Reserve Association.