Profilo
Thomas P. O’Brien advises clients throughout all phases of government investigations and prosecutions encompassing a broad scope of situations such as corporate compliance matters, fraud, and state and federal False Claims Act cases. He serves as both an advocate and counselor for corporations and individuals, guiding them from the start of government interactions to the end of trial proceedings. Tom often carries out internal investigations for corporations and municipal governments with a strategic approach, aiming to prevent clients from potential legal violations or misconduct.
In the field of white collar defense, Tom manages cases of embezzlement, accounting fraud, and bribery, among others, addressing complex and dynamic issues. He represents clients in complex civil actions involving substantial financial amounts and offers advice to foreign state leaders in criminal proceedings. He has robust experience managing cases associated with federal and state False Claims Act statutes (also known as qui tam matters), and the Foreign Corrupt Practices Act. He effectively guides clients through intricate health care fraud issues, as well as other regulatory hurdles.
Tom is a nationally recognized trial attorney. He is a U.S. Fellow with the International Academy of Trial Lawyers, an honor limited to 500 trial attorneys in the United States; a member of the National Trial Lawyers: Top 100; and has been noted by Chambers USA. Tom has tried over 100 criminal and civil cases in federal and state courts throughout the nation. He has represented national and multinational companies in civil actions with billions of dollars in dispute, and has represented individual corporate leaders and foreign heads of state in civil, criminal, and regulatory proceedings. He has deep experience navigating dual civil-criminal proceedings and handling complex, first-of-its-kind matters in multiple jurisdictions, including matters conducted in foreign nations.
Tom previously served as United States Attorney for the Central District of California, a position to which he was appointed by President George W. Bush and unanimously confirmed by the United States Senate. During his term, he oversaw all federal criminal and tax investigations and prosecutions, in addition to all civil matters involving the United States, within the largest federal district in the nation. Under his leadership, his office filed record-breaking felony cases and increased complex case filings by 50 percent, including significant progress in prosecuting organized crime. The office filed the largest gang RICO case in the history of the Department of Justice, the largest RICO case against a motorcycle gang and, for the first time in the nation, seized the gang’s trademark. His office also filed the largest tax restitution case in IRS history.
Before his confirmation as United States Attorney, Tom served as Chief of the Criminal Division for over two years. In this role, he was responsible for several high-profile espionage cases, helped bring the first treason case in the country since World War II, supervised multiple public corruption and civil rights cases, and oversaw some of the largest fraud cases prosecuted in the United States.
Before being selected as Criminal Chief, Tom led the office’s Civil Rights Section, where he investigated and prosecuted numerous cases, including federal hate crimes, human trafficking offenses, and police and prison guard misconduct cases.
Tom’s prosecutorial career began in San Diego County before moving to Los Angeles County as a Deputy District Attorney assigned to the Hardcore Gang Division, where he tried 35 gang murder cases.
After graduating from the United States Naval Academy, he served in the United States Navy as a Radar Intercept Officer in the F-14A Tomcat fighter, completing over 2,000 flight hours and two overseas deployments on active duty. He is a graduate of the United States Navy Fighter Weapons School commonly known as TOPGUN.
Competenze
Esperienze Professionali - Attività Accademiche
- Led the defense of a medical doctor charged in a $355 million federal health care fraud prosecution. After a three-month trial, the jury fully acquitted Tom’s client on all 33 felony counts. All other defendants were convicted on all counts.°
- Led the defense of a U.S. Navy admiral in connection with the federal “Fat Leonard” bribery prosecution, the largest corruption case in the history of the United States Navy. After a four-month trial, the jury could not reach a verdict on any count against Tom’s client, and the court dismissed all charges against the client. The jury convicted all other defendants on all counts.°
- Led the defense of an individual charged in the nation’s first-ever federal “birth tourism” prosecution. Tom negotiated a plea agreement where his client pleaded guilty to only two counts of a 28-count indictment. Despite the government seeking a sentence of 33 months imprisonment, Tom secured a sentence of time-served and minimal supervised release. Tom also recovered for the client several million dollars-worth of assets that had initially been seized by the government in connection with this prosecution.°
- Represented an individual investigated by the Department of Justice for allegedly participating in an insider trading scheme. Tom persuaded the DOJ not to indict his client, even though the DOJ indicted and secured convictions against several other individuals allegedly associated with the scheme.°
- Represented an individual in connection with one of the nation’s first-ever criminal investigations and charges under the Foreign Agents Registration Act (FARA).°
- Obtained a multimillion-dollar pre-litigation settlement on behalf of a client alleging sexual assault.°
- Represented a hospital in connection with an investigation by the Department of Justice and Office of the Inspector General into potential violations of the False Claims Act and federal Anti-Kickback Statute. Despite the government’s initial demand that the hospital pay restitution and fines totaling millions of dollars, Tom was able to persuade the government to drop the matter against his client.°
- Led the defense of a university professor in a high-profile felony prosecution involving alleged labor code violations, which resulted in the charges being dismissed. The case garnered national media attention in what has been described as the first case of its kind.°
- Represented a major national services corporation in a Department of Justice investigation concerning allegations that the company violated the False Claims Act. The investigation was closed by the Department of Justice with no charges being brought.°
- Led a team to effectively defend a local government entity during a two-year DOJ investigation into allegations of corruption in a billion dollar purchasing project.°
- Represented a foreign conglomerate in a high-profile criminal matter involving allegations of international trade secret theft in the Eastern District of Virginia.°
- Spearheaded the internal investigation into serious allegations of fraud against a medical device manufacturer. At the conclusion of the investigation, Tom’s team made a multihour presentation to the government resulting in the termination of the investigation into the client.°
- Assisted in representing a former CEO against allegations that the client engaged in insider trading in connection with a secondary offering. The client was acquitted on all charges at trial.°
- Pioneered a novel settlement strategy for a medical device manufacturer to resolve criminal allegations brought against it in connection with alleged Cal/OSHA violations.°
- Led a federal trial team to a front-page defense victory for a Los Angeles County sheriff’s deputy accused of obstruction of justice, where the jury was unable to reach a verdict on the counts charged.°
- Led a team of attorneys in conducting an internal investigation at the request of a Southern California health center. That investigation, since closed, arose out of allegations that employees of the health center accepted improper benefits in exchange for referrals to certain patient facilities in violation of federal and state anti-kickback statutes.°
- Persuaded the Department of Justice not to file fraudulent billing charges against a physician with a successful medical practice. When Tom was brought onto the case, the investigation had been ongoing for several years, and the government had issued a final plea offer and expressed its intention to indict the client. Within weeks, Tom and his team conducted an investigation and presented new evidence to the Department of Justice. The Department of Justice subsequently allowed the statute of limitations to expire on the charges that it, only weeks earlier, had intended to file.°
- Represented the police chief of a local city who faced civil charges filed by the state Attorney General as part of allegations against an entire city council and several administrators for defrauding taxpayers and wasting taxpayer monies. In a case described by numerous media outlets as one of the biggest corruption cases in the nation, and despite the extreme public outcry attacking his client, Tom and his team convinced the court to dismiss the complaint with prejudice.°
- Represented a local airport commission in an investigation by the Federal Bureau of Investigation into allegations of corruption. Within months of being retained in this case, Tom managed to focus the government on the actions of other individuals and received a letter from the Department of Justice clearing his client.°
°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
Riconoscimenti e Premi
- Listed, The Best Lawyers in America, 2016-2025
- Criminal Defense: White-Collar, 2016-2025
- Litigation – Securities, 2023-2025
- Listed, Chambers USA Guide, Litigation: White-Collar Crime & Government Investigations
- Listed, Lawdragon, “500 Leading Litigators in America,” 2025
- Fellow, Litigation Counsel of America
- U.S. Fellow, International Academy of Trial Lawyers, 2015-2024
- Selected, National Trial Lawyers: Top 100, 2011-2024
- 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)
Formazione
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Laurea magistrale in Giurisprudenza, cum laude, University of San Diego School of Law
- Associate Editor, San Diego Law Review
- B.S., U.S. Naval Academy
- California