About O'Brien Hatfield, PA
After beginning his career at the end of the last century as a prosecutor in Miami, Florida, Attorney Mark J. O’Brien started his own law firm on January 1, 2003. After nearly thirty years, Mr. O’Brien has expanded his firm beyond himself. Now named O’Brien Hatfield, Mr. O’Brien’s law firm has seven lawyers, one paralegal, four legal assistants, two private investigators (a retired IRS CID special agent and a retired DEA special agent), one sentencing mitigation specialist (a former United States Probation Officer), and numerous third-party experts who assist on a case-by-case basis. Mark J. O’Brien, Managing Partner Attorney Mark J. O’Brien is a nationally recognized federal criminal defense attorney with nearly thirty years of experience in criminal courts all throughout the country. After beginning his professional career as a Miami, Florida prosecutor in the late 1990’s, Mr. O’Brien organized his own law firm in 2002 based upon the professional lessons he learned to that point in his life with the goal defending those accused of federal and state crimes with a mix of old school values and new school ideas. He is the firm’s managing partner. During his first decade in private practice from 2002 to 2012, Mr. O’Brien defended individuals and corporations charged with federal crimes throughout federal criminal courts in Florida. From 2012 to the present, Mr. O’Brien has accepted the defense of clients charged in federal criminal courts throughout the entire country, in addition to his previously established federal criminal defense practice in all federal courts in Florida. Case after case, success after success, in federal court after federal court, all throughout the country, has resulted in a growing legacy. To put it simply, Mr. O’Brien wins and, as a result, he is a lawyer in demand. Mr. O’Brien is a licensed member of the Bar of the State of Florida (1998), the Bar of the Commonwealth of Massachusetts (1998), and the Bar of the State of Montana (2023). He has practiced federal criminal defense as a member or a pro hac vice member of the following federal appellate and district courts: • Supreme Court of the United States of America • United States Court of Appeals for the First Circuit • United States Court of Appeals for the Second Circuit • United States Court of Appeals for the Ninth Circuit • United States Court of Appeals for the Eleventh Circuit • United States District Court for the Northern District of Alabama • United States District Court for Alaska • United States District Court for the Eastern District of Arkansas • United States District Court for the Central District of California • United States District Court for the Southern District of California • United States District Court for Connecticut • United States District Court for the Southern District of Florida • United States District Court for the Middle District of Florida • United States District Court for the Northern District of Florida • United States District Court for the Southern District of Georgia • United States District Court for the Middle District of Georgia • United States District Court for the Northern District of Georgia • United States District Court for the Southern District of Illinois • United States District Court for the Southern District of Indiana • United States District Court for Kansas • United States District Court for the Eastern District of Kentucky • United States District Court for Massachusetts • United States District Court for the Eastern District of Michigan • United States District Court for the Western District of Michigan • United States District Court for the Northern District of Mississippi • United States District Court for the Southern District of Mississippi • United States District Court for the Western District of Missouri • United States District Court for Montana • United States District Court for the Southern District of New York • United States District Court for the Northern District of New York • United States District Court for the Western District of New York • United States District Court for North Dakota • United States District Court for Northern District of Oklahoma • United States District Court for Rhode Island • United States District Court for the Middle District of Tennessee • United States District Court for the Eastern District of Texas • United States District Court for the Western District of Texas • United States District Court for the Northern District of Texas • United States District Court for the Eastern District of Virginia • United States District Court for the Eastern District of Washington • United States District Court for the Western District of Washington • United States District Court for the Southern District of West Virginia Mr. O’Brien handles all federal criminal areas of practice, including but not limited to: Tax Fraud, Mail Fraud, Wire Fraud, Bank Fraud, Mortgage Fraud, Securities Fraud, Medicare Fraud, Health Care Fraud, Bribery, IRS Issues, Emb
