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For nearly three decades, B. Stephanie Siegmann ’94 has stood at the forefront of national security and legal battles, evolving from a federal prosecutor to a trusted advisor on cybersecurity and international trade.

For nearly three decades, B. Stephanie Siegmann ’94 has stood at the forefront of national security and legal battles, evolving from a federal prosecutor to a trusted advisor on cybersecurity and international trade.

Throughout her career, she's garnered numerous accolades for her legal expertise and dedication, including recognition by Best Lawyers in America^® (2025) and Super Lawyers (2023–2024). She was named a Go To Lawyer by Massachusetts Lawyers Weekly in cybersecurity/data privacy (2022, 2024) and as a Top Women of Law (2021). Additionally, she received numerous awards for her government and military service, such as the Navy and Marine Commendation Medal and Navy and Marine Corps Achievement Medal.

Now a partner at the Boston office of the law firm Hinckley Allen, Siegmann specializes in high-stakes litigation, internal investigations, and government enforcement proceedings. Additionally, she chairs the International Trade & National Security group and co-chairs the Cybersecurity, Privacy & Data Protection group at the firm.

“My unique background allows me to guide companies through complex challenges, whether they’re facing a cyberattack, navigating national security regulations, conducting internal investigations, or responding to a subpoena,” Siegmann said. “It’s about helping them mitigate risks and find solutions.”

Siegmann explained that her path to law was driven by a promise to honor her late father, Thomas Patrick Mahoney.

“When I was 10 months old, my father, who was serving in the Air Force, was killed by a drunk driver,” Siegmann said. Her mother, who was just 18 years old at the time, survived the accident but was hospitalized for months, leaving Siegmann in the care of her grandparents. At age 12, she learned about her father’s unrealized dream: he had wanted to pursue law.

“From that moment, I knew I wanted to fulfill his dream. But I didn’t realize how hard it would be.”

As a first-generation ÌìÃÀ´«Ã½ student, Siegmann faced significant challenges early on in her academic journey, with financial difficulties forcing her to leave school after her freshman year. She took on a part-time job as a mail clerk at a real estate law firm in Brookline, which quickly evolved into a full-time paralegal position. Then one day, a colleague offered Siegmann a life-changing piece of advice: “Don’t give up. Apply to UMass Boston.”

So, she did.

“It was the best decision that I could have made,” Siegmann said. “[Director of Veterans Affairs] Augusto St. Silva helped me obtain veteran benefits that I didn't even know I was entitled to. No one at [my previous school] had taken the time to help me do that, and it really meant a lot to me. I will always be indebted to UMass Boston for providing me the opportunity to obtain a great education and serve students on the UMass Board of Trustees.”

After earning her bachelor’s degree in history and psychology, Siegmann was able to continue her path toward a legal career, enrolling at Suffolk University Law School. During her second year of law school, Siegmann was selected for the Navy’s Judge Advocate General’s Corps. and accepted a commission as a Naval officer.  Commonly known as the “JAG Corps,” or, simply, “JAG,” the group serves as the legal branch of the United States Navy.

As a Navy JAG, Siegmann chose to work as a prosecutor at the Norfolk Trial Service Office where she handled complex felony cases—murder trials, child abuse investigations—and gained invaluable trial experience. Her service coincided with critical moments in U.S. history, such as the attack on the USS Cole.

“I got to work with numerous exceptional lawyers. I don't think I would have had that experience anywhere else at the time,” she said. “I’m very lucky and privileged to have served in that capacity.”

After leaving the Navy, Siegmann’s career took a defining turn in the wake of the September 11 attacks. She worked as national security prosecutor for more than 18 years at the U.S. Attorney’s Office for the District of Massachusetts culminating in becoming the first female National Security Chief. During her tenure as a national security prosecutor, she prosecuted some of the nation’s most significant cases, from terrorism plots to cyber intrusions. Among them, she investigated a groundbreaking case in 2011 involving an individual plotting to use C4 explosives in remote-controlled aircraft, which helped prompt Federal Aviation Administration regulations on drones.

She also led the prosecution of a decade-long conspiracy in which Chinese operatives illegally exported sensitive U.S. semiconductor technology to China. Other notable cases include Siegmann’s prosecution of individuals involving in obstructing the investigation of the 2013Boston Marathon bombings, thwarting an ISIS beheading plot in Massachusetts, and disrupting an illegal procurement network supplying parts to Iran’s nuclear weapons program

“Some of these investigations were really instrumental in ensuring that we didn't have another terrorist attack in Massachusetts,” said Siegmann. “I felt privileged to have some role in hopefully preventing terrorist attacks and safeguarding U.S. national security.”

As a leader at Hinckley Allen, Siegmann now focuses on helping businesses safeguard against cybersecurity threats. She advises on everything from ransomware attacks to insider threats and complex export control regulations, as well as addressing the opportunities and risks associated with artificial intelligence (AI).

“[AI] has really supercharged cybercrime. AI tools allow threat actors to scan, identify, and weaponize vulnerabilities in target networks far quicker than ever better. AI tools have also been used to craft more persuasive phishing emails, create voice clones to orchestrate fraud schemes, and develop malicious code and new variants of malware that are less likely to be detected by cybersecurity tools” she said. “But on the flip side, organizations need to understand how to harness AI tools for cyber defense and establish guardrails and mitigate the risks of using these tools by implementing an AI governance policy.”

While her role at Hinckley Allen marks a departure from her work as prosecutor, Siegmann said her transition has offered her the opportunity to leverage her unique trial experience and skills to help businesses and individuals deal with evolving threats and a complex regulatory enforcement landscape.

“In private practice, I have a far more diversified practice that not only involves criminal investigative matters, but also navigating cybersecurity issues as well as privacy concerns, protection of intellectual property, and complex governmental regulations. As a result, I enjoy my new role as a trusted advisor to companies where every day allows me to use my expertise to address new challenges and help people confronting legal problems.”