Background
I'm Christopher O'Brien, and I've spent over fourteen years in the legal profession — most of them in the courtroom. My career has taken me from tax consulting to felony prosecution to the Massachusetts Attorney General's Office, and now to my own practice focused on criminal and administrative appeals.
That trajectory wasn't accidental. Every role taught me something different about how the legal system works — and where it fails. As a prosecutor, I learned how cases are built, what evidence juries find compelling, and how the law is applied at every stage from investigation to sentencing. Now, as a defense attorney, I use that knowledge to identify the errors that can change outcomes on appeal.
Prosecution Experience
I served as an Assistant Attorney General in the Criminal Bureau of the Massachusetts Attorney General's Office, where I rose to a managing attorney role. I specialized in complex financial investigations — larceny, embezzlement, money laundering, and insurance fraud — and prosecuted cases from investigation through trial and sentencing.
Before that, I spent over three years as a felony prosecutor in Rockingham County, New Hampshire, handling everything from robbery and arson to drug trafficking conspiracies. I was appointed to a specialized Drug Prosecution Team and used my tax law background to lead large-scale financial crime cases.
I've also prosecuted misdemeanors in Salem, New Hampshire, where I managed hundreds of cases and conducted multiple bench trials per week. This breadth of experience — from misdemeanors to complex white collar investigations — gives me a comprehensive understanding of the criminal justice system at every level.
Defense & Appellate Work
As Senior Trial Counsel at the Law Offices of Matthew W. Peterson, I handled a broad caseload spanning criminal defense, administrative law, civil litigation, and appeals at both the trial and appellate levels. I advised the firm on trial strategy, trained associates, and participated in firm management.
In February 2026, I opened the Law Office of Christopher B. O'Brien to focus on what I do best: criminal and administrative appeals. My practice is built on the conviction that every person deserves a rigorous, thorough review of their case — especially when their liberty is at stake.
Education & Training
Juris Doctor — New England Law | Boston
Dean's List all semesters. Comment and Note Editor, New England Journal on Criminal and Civil Confinement. Dean's Scholarship recipient.
B.A. Political Science — Fairfield University
Dean's List. International study at the University of International Business and Economics in Beijing, China.
International Comparative Law — National University of Ireland
Six-week program at the Irish Centre for Human Rights in Galway.
Specialized Training
- DOJ Money Laundering and Asset Recovery Seminar (2024)
- U.S. Secret Service Digital Evidence for Prosecutors Course (2022)
- MA Attorney General's Cyber Crime Conference (2022, 2023)
- ATF Arson for Prosecutors Course (2021)
Bar Admissions
- Massachusetts State Bar (2011)
- New Hampshire State Bar (2018)
- United States District Court, District of Massachusetts (2022)
Publications
America's Useless Torture Statute: How the USA PATRIOT Act and Special Maritime Jurisdiction Can Be Used to Circumvent the Federal Prohibition on Torture, 37 New Eng. J. on Crim. & Civ. Confinement 349 (Spring 2011).