Thomas P. O’Brien

Thomas P. O’Brien is a nationally renowned trial attorney based in Los Angeles, California. He has nearly three decades of experience in complex criminal and civil matters in both private practice and government service.

Tom O’Brien has successfully tried more than 100 civil and criminal cases in multiple state and federal jurisdictions. His client roster includes multiple Fortune 500 firms as well as individual corporate executives and foreign heads of state. He has considerable experience managing dual civil-criminal matters, multi-jurisdiction cases in the U.S. and abroad, and first-of-their-kind legal matters that present novel legal questions in unsettled areas of law.  

Current Role — Partnership With Ellis George Cipollone O’Brien Annaguey LLP

Thomas P. O’Brien is currently a partner with Ellis George Cipollone O’Brien Annaguey LLP, working out of the firm’s Los Angeles-area offices. 

He represents clients at every phase of the investigative process as well as in active prosecutions. He has been involved in matters involving allegations of health care fraud, violations of the Foreign Corrupt Practices Act (FCPA), and state and federal violations of the False Claims Act (qui tam), as well as corporate compliance matters brought by the U.S. Department of Justice, Securities and Exchange Commission, and other state and federal legal and regulatory authorities. 

Mr. O’Brien also performs internal investigations for corporations related to wrongdoing or possible violations of law by employees, shareholders, contractors, and other parties; and provides advice to clients on complicated white-collar matters such as accounting embezzlement and fraud. 

Service With the Los Angeles County District Attorney’s Office and U.S. Department of Justice 

Tom O’Brien began his prosecutorial career as a deputy district attorney in the Los Angeles County District Attorney’s office. There, he tried 35 gang-related murder cases as a member of the office’s Hardcore Gang Division.

Mr. O’Brien subsequently served as an Assistant U.S. Attorney in the Central District of California and later as Chief of the Civil Rights Section. An unusually hands-on Chief, he personally prosecuted human trafficking, police misconduct, and federal hate-crimes cases. He repeated this pattern later as Chief of the Criminal Division, where he personally oversaw the country’s first treason case since World War II and charged multiple cyber-crime statutes for the first time on record.

Thomas P. O’Brien’s government service culminated with his tenure as the United States Attorney in the Central District of California — the country’s largest federal court jurisdiction — from 2007 to 2009. With a purview that included all federal criminal, tax, and civil matters in the Central District, he increased the rate of complex case filings by 50 percent and oversaw the largest gang-related RICO case in DOJ’s history.

Career in Private Practice

After leaving government service in 2009, O’Brien transitioned to private criminal and civil law trial practice. His first role was a partnership with Paul, Hastings, Janofsky & Walker, working out of the firm’s Los Angeles offices for a decade. He then accepted a partnership with Browne George Ross LLP, also working out of Los Angeles.

In both roles, Thomas O’Brien worked on complex civil and white-collar criminal matters for a diverse array of individual and corporate clients. O’Brien’s notable representations and outcomes since entering private practice have included:

  • Representing a hospital in a federal matter related to potential violations of the federal Anti-Kickback Statute and the False Claims Act.
  • Representing a high-profile national services corporation in a DOJ investigation into allegations of False Claims Act violations. The investigation closed with no charges filed.
  • Defending a local government entity in a DOJ investigation into alleged corruption in a major purchasing project.
  • Leading an internal investigation of fraud allegations against a medical-device firm and persuading the government to terminate its investigation in the matter.
  • Managing a novel settlement strategy on behalf of a medical-device firm to resolve the criminal allegations connected to alleged OSHA violations.
  • Uncovering new evidence in a long-running DOJ investigation of a physician accused of fraudulent medical billing and persuading the government not to file planned charges.

Professional Recognition

Tom O’Brien has earned numerous accolades and awards in the course of his career. 

He is a current U.S. Fellow with the International Academy of Trial Lawyers — one of just 500 trial attorneys in the U.S. given this honor. Tom is also a member of the National Trial Lawyers: Top 100 and was recognized by Chambers USA as an attorney with “fantastic instincts and courtroom skill.” 

While in government service, Mr. O’Brien was:

  • Named Deputy District Attorney of the Month Award for his successful prosecution of two gang-related murder cases in July 2000
  • Awarded the Attorney General’s Award for Exceptional Service for his contribution to the investigation and prosecution of gang-related hate-crime murders in Los Angeles in 2007
  • Presented with the 2008 Immigration and Customs Enforcement Assistant Secretary’s Award for Excellence in Law Enforcement
  • Given accolades from at least a dozen government entities and law enforcement organizations, including the FBI, USPS, IRS, U.S. Marshal’s Office, U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives, U.S. Secret Service, the Los Angeles Police Department, the Los Angeles City Council, the Los Angeles City Attorney’s Office, and the Santa Barbara District Attorney’s Office

Philanthropy and Community Service

Thomas P. O’Brien holds several roles with the American Bar Association. He served as the vice-chair of the ABA Section of International Law and sat on the organization’s International Anti-Corruption Committee, Steering Committee, and Asia Regional Forum.

Thomas PO Brien Profile ImageO’Brien also served as a member of the Legal Advisory Committee for the Anti-Defamation League.

He is a former board member of the Chandler School in Pasadena, California; a former board member of the Legal Aid Foundation of Los Angeles, and the former chair of the Cyber/Intellectual Property Subcommittee of the Attorney General’s Advisory Committee.

Early Life, Education, and Military Service

Thomas O’Brien was raised near Boston. He attended the United States Naval Academy in Annapolis, Maryland, and graduated with a bachelor’s degree in 1981.

After leaving the U.S. Naval Academy, O’Brien logged more than 2,000 flight hours in the F-14A Tomcat fighter as a Radar Intercept Officer, completing two overseas deployments on active duty. He is a proud graduate of the United States Navy Fighter Weapons School, or TOPGUN — the elite pilot training school popularized by the film of the same name. 

Thomas O’Brien left Navy service in 1987 and briefly worked as a securities trader. He matriculated at the University of San Diego School of Law in 1990 and graduated with honors in 1993, having served as an associate editor of the San Diego Law Review.