Mr. Carnathan is a founder and Co-Managing Partner of O'Connor, Carnathan and Mack, LLC, where Mr. Carnathan focuses his practice in complex business litigation with a particular emphasis on insurance coverage, closely held business disputes, financial services and trust and estate litigation.

Since 1993, although Massachusetts based, Mr. Carnathan has been litigating cases all over the country, from Texas to Minnesota and from California to Maine. He has tried or arbitrated over 25 cases in the state and federal courts of Connecticut, Delaware, Maine, Massachusetts, and New Hampshire.

Mr. Carnathan has been rated Preeminent by Martindale Hubbell for many years. He has been selected as a “Super Lawyer” by Boston Magazine since 2008, is a 2016 Irish Legal 100 Honoree, and has been listed in U.S. News & World Report’s Best Lawyers in America since 2016.

Mr. Carnathan is a regular commentator on legal issues and has published many articles throughout his career. He is the author of Massachusetts Bad Faith Insurance Litigation. The second edition of this book, which was published in March 2020, offers a complete guide to bad faith insurance cases under the Massachusetts bad faith insurance practices statute, M.G. L. c. 176D. Mr. Carnathan is also a Senior Fellow of the Litigation Counsel of America.  He has previously served as a FINRA arbitrator and has been a hearing officer for the Massachusetts Board of Bar Overseers since 2015.

Mr. Carnathan is admitted United States District Court for the District of Maine, States District Court for the District of Massachusetts, United States District Court for the District of New Hampshire; United States Court of Appeals for the First Circuit, United States Court of Appeals for the Fifth Circuit, and United States Court of Appeals for the Second Circuit.

Mr. Carnathan received his Master of Laws with an emphasis on intellectual property from Harvard Law School, his Juris Doctor, summa cum laude from University of Maine School of Law, and his BA, magna cum laude, from Bowdoin College.