A nationally recognized authority on criminal punishment, Professor O'Hear teaches criminal law and related courses. He is the author or coauthor of more than seventy-five scholarly articles, books, and book chapters on sentencing, criminal procedure, and other legal topics. His books include The Failed Promise of Sentencing Reform, Prisons and Punishment in America: Examining the Facts, and Wisconsin Sentencing in the Tough-on-Crime Era: How Judges Retained Power and Why Mass Incarceration Happened Anyway.
Professor O'Hear is a graduate of Yale College and Yale Law School, where he was editor-in-chief of the Yale Journal of Law & the Humanities and an editor of the Yale Law Journal. Following law school, he clerked for United States District Court Judge Janet Bond Arterton in New Haven, Connecticut. He then practiced civil and criminal litigation at Sonnenschein Nath & Rosenthal in Chicago. He joined the Marquette Law School faculty in 2000, and served as the Law School's first Associate Dean for Research from 2008 to 2015.
Professor O'Hear was a member of the Milwaukee Fire and Police Commission from 2010 to 2016. He has been awarded the Robert W. Warren Public Service Award by the Eastern District of Wisconsin Bar Association, and is an elected member of the American Law Institute.