William Frentzen, an accomplished trial lawyer who formerly served as chief of the Corporate and Securities Fraud Unit for the U.S. Attorney’s Office for the Northern District of California (NDCA), is a partner in Morrison Foerster’s Trial and Investigations + White Collar Defense Groups.

William represents companies and their executives in internal and government investigations, white collar criminal defense matters, and parallel civil litigation related to allegations of corporate fraud, securities fraud, public corruption, intellectual property crimes, crisis response related to cyber breaches, money laundering, healthcare fraud, digital currency crimes, tax crimes, cybercrime, Racketeer Influenced and Corrupt Organization (RICO) Act violations, and environmental crimes, among others.

Over the course of his career, William has successfully tried over 40 federal criminal and civil jury trials around the country, including some of the longest and most complex criminal cases in the NDCA. His trial capabilities were recognized through his appointment as senior trial counsel for the NDCA, a position created in acknowledgment of William’s unique ability to try cases. He has never lost a jury trial in which he served as first-chair. William’s trial experience includes securing conviction of a chief financial officer related to accounting and securities fraud charges arising out of the $11 billion sale of a software company, the largest fraud case in the history of the NDCA. He has also achieved several high-profile criminal resolutions, including the first-ever criminal prosecution for violating the Lobbying Disclosure Act against an infamous lobbyist and the conviction of two corrupt federal agents for stealing and extorting digital currency during their investigation of the Silk Road dark market website. He also served as an adjunct professor at UC Berkeley School of Law, where he taught civil trial practice.

William has represented cryptocurrency platforms and other companies through exploit and cybersecurity attacks and asset recovery, including representing a company through the largest digital asset recovery in decentralized finance history. He also serves as an advisor for the capital fund of Haun Ventures, an investment firm focused on web3 ventures, tokens, and projects related to blockchain technology, digital currency, and crypto assets.

Before joining MoFo, William spent over 20 years at the U.S. Department of Justice (DOJ), where he most recently served as chief of the Corporate and Securities Fraud Unit for NDCA. Prior to that he served as chief of the Corporate Fraud Strike Force, as senior trial counsel, and as chief of the Organized Crime Strike Force for that office, and he also developed and supervised the country’s first cryptocurrency crime coordinator position within a U.S. Attorney’s Office. William has also served as an assistant United States attorney (AUSA) in the U.S. Attorney’s Offices for the District of Columbia and the Southern District of Georgia and as associate independent counsel in the Office of Independent Counsel.

Since joining private practice, William has been recognized by leading industry and business publications, including Financial Times, which named him a “Commended Individual” in the Innovative Lawyers in Cyber Security & Data Protection category of its 2023 North America Innovative Lawyers report. He was recognized for his role in negotiating the return of nearly $200 million in digital assets for Euler, three weeks after these assets were stolen, completing one of the largest recoveries in decentralized finance history. Further, William was named to Daily Journal’s 2024 list of Leading Commercial Litigators relating to the successful handling of multiple civil litigation matters, including a jury trial victory, two granted summary judgment motions, and his work on the Euler matter mentioned above.

William also received numerous awards for his exceptional trial work at DOJ, including, among others, the Attorney General’s Distinguished Service Award, the DOJ Director’s Award for Superior Performance by a Criminal AUSA, and the FBI Director’s Award for Excellence, in addition to various other awards and commendations from federal and state agencies. He was also recognized as a California Attorney of the Year by The Recorder following a five-month racketeering jury trial.

Throughout his time as a prosecutor, William has coordinated with a variety of state, local, and federal law enforcement partners, including the U.S. Securities Exchange Commission (SEC), Federal Bureau of Investigation (FBI), Internal Revenue Service (IRS), Commodity Futures Trading Commission (CFTC), Federal Trade Commission (FTC), Office of Foreign Assets Control (OFAC), and Financial Crimes Enforcement Network (FinCEN), among others. He has also worked with numerous global law enforcement agencies, including INTERPOL, Europol, the UK Serious Fraud Office, and the UK National Crime Agency, among others.

William received his J.D. cum laude from Tulane Law School, where he also received a certificate in environmental law, and his B.A. from New College of the University of South Florida.

Representative Experience

Private Litigation Experience

• Obtained a rare jury verdict in a Clean Water Act trial in the Central District of California involving allegations of years of runoff into navigable waters, applying a recent Supreme Court decision regarding pollution point sources.
• Obtained a complete defense victory through summary judgment for a leading transportation technology company against a prominent venture capital fund that alleged fraud and contractual interference.
• Secured a favorable settlement after jury selection in a trial for a major biosciences company and founders, executives, and board members in a lawsuit filed in San Diego Superior Court alleging fraud, breach of contract, and tortious interference claims, which sought damages of $400–700 million.
• Negotiated the return of more than $220 million in digital assets for a leading decentralized finance (DeFi) platform, three weeks after these assets were stolen, completing one of the largest recoveries in DeFi history.
• Representing OpenAI and two current executives in a claim for breach of contract, promissory estoppel, breach of fiduciary duty, and unfair competition brought by Elon Musk.
• Representation of a DeFicrypto exchange in relation to a major exploit resulting in the misappropriation of over $110 million, including negotiating return of most of the funds; assisting in identifying the attacker, leading to his conviction; and bringing a lawsuit against the attacker for return of remaining funds.
• Representation of a technology company through discovery and repair of a defect that could have been exploited to adversely impact customers and result in litigation but was handled in a manner avoiding any impact to customers.
• Negotiated the safe return of Tigran Gambaryan, a former decorated IRS Criminal Investigations agent who was unlawfully lured, detained, and prosecuted by the Nigerian government. The matter involved coordination with local counsel in Nigeria as well as other law firms and entities in the United States to raise awareness of his detention, bring pressure for his release, craft his legal strategy and trial defense, and pursue legal recourse against those who unlawfully detained him. All charges were dismissed against the client.
• Representation of technology company against allegations of false advertising by City Attorney’s Offices. Representation concluded without any claims being brought against the client.
• Representation of companies and executives through investigations by the U.S. Department of Justice. Representations concluded without charges being brought against the client.
• Representation of companies and executives in regulatory investigations and cases investigated and brought by the CFTC and the SEC.
• Representation of companies through investigations by state and local law enforcement.
• Representation of companies in highly sensitive matters involving internal fraud investigations and involuntary and negotiated departures of the chief executive and other senior officers.

Government Experience

• Brought accounting and securities fraud charges against a chief executive officer, chief financial officer, and founder arising out of the $11 billion sale of a software company, which led to the conviction of the chief financial officer and became the largest fraud case in the history of NDCA.
• Brought money laundering, conspiracy to commit international money laundering, and operating an unlicensed money exchange charges against an unregistered digital currency exchange, BTC-e, and its primary operator. Brought novel charges for the infamous hack of the Mt. Gox cryptocurrency exchange.
• Seized billions of dollars in digital currency, one of the largest seizures in U.S. history, related to the Silk Road digital black-market platform.
• Brought money laundering, computer intrusion, and conspiracy to commit wire fraud charges against the perpetrators of a major cyber breach involving VIP customer accounts of a large social networking service and cryptocurrency fraud. This was one of the most rapidly investigated and charged cyber incidents of recent times.
• Conducted an investigation into conspiracy to commit money laundering and conspiracy to distribute narcotics into the largest and longest-running darknet market, Hydra Market, which accounted for approximately 80% of all cryptocurrency transactions on the darknet generally.
• Brought securities fraud charges against an online cryptocurrency investment manager and its principal related to a fraudulent investment scheme valued at $20 million.
• Brought theft of trade secrets charges against the chief engineer of a multinational transportation company regarding the misappropriation of self-driving vehicle technology.
• Brought public corruption charges against the heads of various municipal and public utilities operations in California.
• Brought bribery and honest services charges against a California state senator and organized crime and RICO charges in one of the most significant organized crime cases in history, involving the infamous Raymond “Shrimp Boy” Chow.