Colleen O'Connor

Colleen represents clients in white collar criminal matters, internal investigations, and securities enforcement actions across various industries, including health care, pharmaceuticals, e-commerce, nuclear, and financial services. She defends clients facing U.S. Department of Justice (DOJ), Securities and Exchange Commission (SEC), and state attorneys general offices investigations and enforcement matters related to allegations of fraud and corruption.

Colleen has extensive experience advising clients on the False Claims Act (FCA), including navigating past enforcement actions, investigating alleged misconduct, and developing solutions for resolution. She is also well versed in conducting and managing internal investigations for clients on sensitive issues and counseling clients on strategic compliance-related solutions.

Before attending law school, Colleen worked at the Manhattan District Attorney’s Office in the Trial Bureau as a trial preparation assistant. During her two years there, she investigated a range of cases from identity theft to murders, assisted prosecutors in multiple homicide and sexual assault trials, and collaborated with prosecutors on numerous cases from arrest through sentencing.

• Routinely represents companies in enforcement actions brought by the SEC, DOJ, and the Massachusetts Attorney General’s Office involving allegations such as insider trading, securities fraud, money laundering, and financial fraud.
• Represents a major health care company during a state attorney general investigation concerning False Claims Act allegations made by a whistleblower.
• Led an independent investigation into claims of sexual misconduct and discrimination at a consulting firm.
• Represented an investment banking firm in an investigation by the SEC involving allegations of violations of federal securities laws, leading to no charges filed against the company.
• Defended a CEO in a criminal case initiated by the DOJ concerning fraud allegations, including tax evasion, wire fraud, and money laundering.
• Represented a pharmaceutical company in connection with an indictment brought by a grand jury, civil lawsuit joined by the DOJ, and Federal Trade Commission (FTC) investigation involving allegations of wire fraud, mail fraud, and health care fraud, leading to an agreement with the DOJ, FTC, and U.S. state attorneys general to resolve criminal charges and civil complaints.

• Best Lawyers in America®: Ones to Watch: Commercial Litigation (2026), Criminal Defense: White-Collar (2026), Health Care Law (2026)