Profile
Thomas P. O’Brien is a nationally recognized trial lawyer and Co-Chair of Greenberg Traurig’s White Collar Defense & Special Investigations Practice. He represents companies and individuals in consequential civil disputes, government investigations, and criminal prosecutions. Tom has tried more than 100 civil and criminal cases in federal and state courts across the country and has represented national and multinational companies in civil matters involving billions of dollars. A former United States Attorney and Criminal Chief for the Central District of California, he brings decades of courtroom experience, government insight, and practical judgment to his clients.
Tom maintains an active complex civil trial and litigation practice, serving as lead or co-lead counsel in high-exposure commercial, statutory, constitutional, and government-related disputes. He also represents corporations, boards, executives, and individuals in government investigations and white collar matters. Drawing on decades of experience seeing how evidence, witnesses, lawyers, and legal theories perform under the pressure of trial, Tom evaluates not only the legal merits of a matter but also the opposing parties and counsel, key witnesses, institutional pressures, business realities, and other factors likely to shape its outcome. This perspective informs his assessment of risk and helps him determine whether to litigate, negotiate, or pursue a resolution.
Tom’s wide-ranging trial experience includes complex civil disputes, health care and financial fraud, public corruption, civil rights, organized crime, and other matters. In two recent back-to-back federal jury trials, he secured the acquittal of a physician on all 33 felony counts after a nearly three-month health care fraud trial and represented the only defendant not convicted in the four-month Navy “Fat Leonard” bribery trial. The government later declined to retry his client, and the remaining charges were dismissed with prejudice. Earlier in his career, as a Los Angeles County Deputy District Attorney assigned to the Hardcore Gang Division, Tom tried approximately 35 gang murder cases. His courtroom experience also informs his counseling and investigations practice, including matters involving the False Claims Act, Foreign Corrupt Practices Act, fraud, securities and accounting issues, bribery and public corruption, tax, corporate compliance, and related civil, criminal, regulatory, and business concerns.
Tom previously served as United States Attorney for the Central District of California, one of the nation’s largest federal judicial districts. Appointed by President George W. Bush and unanimously confirmed by the United States Senate, he oversaw federal criminal and tax investigations and prosecutions, as well as civil matters involving the United States throughout the district. He previously served as Chief of the Criminal Division and Chief of the office’s Civil Rights Section, remaining an active courtroom lawyer throughout his Department of Justice leadership. Before becoming a lawyer, Tom graduated from the United States Naval Academy and served as a Naval Flight Officer in the F-14A Tomcat, completing more than 2,000 flight hours and two overseas deployments. He also graduated from the United States Navy Fighter Weapons School, commonly known as TOPGUN.
الاختصاص
الاختصاص
- Serves as lead counsel to a major global automobile manufacturer in complex litigation arising from a dealership dispute.
- Serves as co-lead trial counsel for a national real estate company in federal litigation involving claims under federal anti-trafficking laws and related state-law claims.
- Represents a major federal government contractor in a constitutional challenge to newly enacted California legislation regulating federal immigration detention facilities.
- Represents a federally recognized Indian tribe in federal litigation against a California county involving access to tribal lands, governmental authority, and related constitutional and jurisdictional issues.
- Represented national and multinational companies in complex civil actions involving billions of dollars in claimed exposure.
- Obtained a multimillion-dollar pre-litigation settlement on behalf of a client asserting significant civil claims.
- Represented a municipal police chief in highly publicized civil litigation brought by the California Attorney General, obtaining dismissal of the complaint with prejudice.°
- Led the defense of a physician charged in a $355 million federal health care fraud prosecution. Following a nearly three-month trial, the jury acquitted the client on all 33 felony counts. The client was the only individual defendant acquitted.°
- Led the defense of a U.S. Navy Rear Admiral in the federal "Fat Leonard" bribery prosecution. Following a four-month jury trial, Tom's client was the only defendant not convicted. The government subsequently elected not to retry him and requested dismissal of the remaining charges, which the court dismissed with prejudice.°
- Assisted in representing a former public-company CEO in a federal insider-trading prosecution that resulted in acquittal on all charges.
- Led a federal trial team defending a Los Angeles County Sheriff's deputy charged with obstruction of justice, resulting in a hung jury.°
- Persuaded the Department of Justice not to indict a client investigated for alleged insider trading even though DOJ prosecuted and obtained convictions against other individuals allegedly involved in the scheme.°
- Represented a hospital in a DOJ and Office of Inspector General investigation involving the False Claims Act and federal Anti-Kickback Statute. After initially seeking millions of dollars in restitution and penalties, the government dropped the matter against the client.°
- Led an internal investigation for a medical device manufacturer and presented the findings to the government, resulting in termination of the investigation into the client.
- Persuaded DOJ not to bring fraudulent-billing charges against a physician after joining an investigation in which the government had already presented a final plea offer and indicated its intention to indict.°
- Led the defense of a local governmental entity in a two-year DOJ investigation concerning alleged corruption in a billion-dollar procurement project.
- Represented a national services company in a False Claims Act investigation that DOJ closed without charges.°
- Represented a foreign conglomerate in a high-profile federal criminal matter involving alleged international trade-secret theft.
- Represented an individual in one of the nation's earliest federal criminal investigations involving the Foreign Agents Registration Act.°
°The above representations were handled by Mr. O’Brien prior to his joining Greenberg Traurig, LLP.
- U.S. Department of Justice, 2000-2009
- U.S. Attorney for the Central District of California, 2007-2009
- Chief, Criminal Division, Central District of California, 2005-2007
- Chief, Civil Rights Division, Central District of California, 2003-2005
- Assistant U.S. Attorney, Central District of California, 2000-2007
- Deputy District Attorney, Hardcore Gang Division, Los Angeles County, 1994-2000
- F-14A Tomcat Radar Intercept Officer, U.S. Navy, 1983-1994
التكريمات والأدوار القيادية
- Listed, The Best Lawyers in America, 2016-2027
- Criminal Defense: White-Collar, 2016-2027
- Litigation – Securities, 2023-2027
- Listed, Chambers USA Guide, Litigation: White-Collar Crime & Government Investigations, 2015-2026
- Listed, Lawdragon, “500 Leading Litigators in America,” 2025-2027
- Fellow, Litigation Counsel of America
- U.S. Fellow, International Academy of Trial Lawyers, 2015-2024
- Selected, National Trial Lawyers: Top 100, 2011-2024
- Listed, Super Lawyers magazine, Southern California Super Lawyers, 2025
- Listed, Daily Journal, “Top White Collar Lawyers,” 2022, 2023, 2024
- Listed, Los Angeles Business Journal, “Leaders of Influence: Litigators & Trial Attorneys,” 2022
- Listed, Los Angeles Times, “Business of Law: Trends, Updates, Visionaries: Legal Visionaries,” 2022
- Recipient, Immigration and Customs Enforcement Assistant Secretary’s Award for Excellence in Law Enforcement, 2008
- Recipient, Anti-Defamation League Pacific Southwest Region, “Helene and Joseph Sherwood Prize for Combating Hate,” 2007
- Recipient, Attorney General’s “Award for Exceptional Service,” 2007
- Recipient, Los Angeles County Association of Deputy District Attorneys, “Prosecutor of the Month Award,” 2000
- Member, Trial Law Institute
- Member, Diversity Law Institute
- Member, National Association of Criminal Defense Lawyers
- Former Vice-Chair, ABA Section of International Law, International Anti-Corruption Committee, Steering Committee, Asia Regional Forum
- Former Member, Legal Advisory Committee for the Anti-Defamation League
- Former Board Member, Chandler School in Pasadena, California
- Former Chair, Attorney General’s Advisory Committee’s Cyber/Intellectual Property Subcommittee
- Former Board Member, Legal Aid Foundation of Los Angeles (LAFLA)
المؤهلات المهنية
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J.D., cum laude, University of San Diego School of Law
- Associate Editor, San Diego Law Review
- B.S., U.S. Naval Academy
- California