Sheila A.G. Armbrust

SHEILA ARMBRUST is a former federal prosecutor with extensive investigations and trial experience. Companies, boards, and individuals, often in moments of crisis, retain Sheila to assist them in conducting internal investigations and responding to investigative demands from the Department of Justice (DOJ), Securities and Exchange Commission (SEC), Federal Trade Commission (FTC), and State Attorneys General. Sheila also represents companies and individuals in high-stakes litigation in federal court. She counsels clients in the technology, artificial intelligence (AI), medical device, life sciences, and financial services sectors, and she advises companies on their compliance programs.

“Sheila is someone who masters the facts of her cases and is able to translate them to prosecutors in a way that is extremely impressive. She really gets the job done — she is an exceptional attorney.”
Chambers USA 2025

Sheila has been recognized by Chambers USA for her work in California Litigation: White-Collar Crime & Government Investigations (2024–2025).

Sheila rejoined Sidley after serving in trial-level and leadership positions in the U.S. Attorney’s Office for the Northern District of California. While at the U.S. Attorney’s office, she was a white collar prosecutor who led teams investigating and prosecuting crimes affecting the safe delivery of healthcare, including securities fraud, mail and wire fraud, violations of the Food, Drug, and Cosmetic Act, trade secret theft, trademark violations, computer fraud and abuse, money laundering, and drug trafficking.

• Lead counsel for money services business defending against federal and state law claims involving customer data.
• Representing an American biopharmaceuticals company and several executives in connection with DOJ and SEC investigations related to the development a cutting edge drug. Successfully convinced the DOJ to drop the investigation. 
• Represented an artificial intelligence company in DOJ and SEC investigations. Successfully closed the investigation without enforcement action from both government agencies.
• Representing an autonomous vehicle company in crisis management planning in the aftermath of DOJ and SEC investigations. 
• Representing the Special Committee of the board of an online video game company in a DOJ and state AG investigation.
• Representing fintech and financial services companies in DOJ investigations in connection with PPP loans. Successfully convinced the DOJ to decline intervention. 
• Representing life sciences company in a DOJ investigation involving allegations of off-label promotion and kickbacks.
• Trial counsel for a telecommunications client in federal RICO litigation who successfully moved to decertify a class of hundreds of thousands of potential litigants.
• Representing a leading public company retailer in internal and government investigations relating to management of supply chain issues.
• Representing a trade association in a highly publicized investigation by the California Attorney General involving allegations of fraud in connection with claims about the recyclability of plastics.
• Represented a blockchain technology company in responding to DOJ investigations.
• Represented a cybersecurity company in a trade secret misappropriation investigation.
• Represented the independent directors of the board of a medical device company in DOJ investigation.
• Represented a pharmaceutical manufacturer in lengthy criminal and civil investigations involving allegations of off-label promotion and kickbacks.

• San Francisco chair, SidleyWomen

• Obtained declination of DOJ investigation and voluntary dismissal of civil lawsuit for a not-for-profit scientific institution in an FCA matter.
• Obtained compassionate release from federal prison sentence for client facing more than 16 years for a first-time criminal offense.
• Obtained a state court order to seal arrest record for client who was factually innocent of crimes for which she was arrested but not charged.
• Obtained asylum for woman and her minor children from Mexico.