Alena Mosier has been appointed Deputy State’s Attorney for the St. Mary’s County State’s Attorney’s Office, State’s Attorney Jaymi Sterling announced.
Since joining the office in 2023, Mosier has served as a founding member of Sterling’s administrative team and has prosecuted some of the office’s most significant violent crime and special victim cases. She previously held roles as Chief of Legal Operations and District Court and as a Senior Assistant State’s Attorney. In her new position, she will continue overseeing attorney training and administrative policies while maintaining an active caseload in both District and Circuit Courts.
Sterling praised Mosier’s leadership and commitment. “Alena has consistently demonstrated exceptional leadership, impeccable trial skills, and an unmatched commitment to justice,” she said. “I am grateful for her dedication and hard work, and I am thrilled she is committed to serving our community in this new role as we continue to work together to protect the citizens of St. Mary’s County.”
Mosier brings extensive prosecutorial experience to the deputy position. She previously served as a Special Assistant U.S. Attorney in the Violent Organized Crime Unit of the U.S. Attorney’s Office for the District of Maryland. She began her career as an Assistant State’s Attorney in Anne Arundel County, where she specialized in violent crimes, domestic violence, sexual assault and human trafficking cases.
She graduated from Florida State University with a Bachelor of Science in Political Science and Philosophy and earned her Juris Doctor from Wake Forest University School of Law. Following law school, she clerked for the Honorable Joan E. Ryon of the Montgomery County Circuit Court.
Mosier has been recognized for her work in St. Mary’s County. In 2026, she was named the County’s Law Enforcement Officer/Prosecutor of the Year by the St. Mary’s County Department of Aging & Human Services, the Triad/SALT Council, the Optimist Clubs of St. Mary’s and the State’s Attorney’s Office. In 2021, she received the Victoria F. Gelfman Legal Excellence Award as a rising Maryland Assistant State’s Attorney.
The Deputy State’s Attorney position is a key leadership role in the office, assisting the State’s Attorney in managing operations and overseeing complex prosecutions. Mosier’s promotion reflects the office’s focus on experienced prosecutors who can handle high-profile cases while contributing to administrative leadership.
St. Mary’s County, like much of Southern Maryland, faces challenges with violent crime, domestic violence and other serious offenses. The State’s Attorney’s Office plays a critical role in holding offenders accountable while supporting victims and maintaining public safety. Mosier’s background in special victim cases and violent crime prosecutions positions her well to continue that work in a leadership capacity.
Her appointment comes as the office continues to address the needs of a growing county with a mix of rural communities, military families near Naval Air Station Patuxent River and increasing development. Strong prosecutorial leadership is essential for maintaining trust in the justice system and ensuring effective case outcomes.
Mosier’s recognition as Prosecutor of the Year and her previous awards highlight her dedication to the profession and her impact on the community. Her experience across federal, state and local levels brings a broad perspective to the deputy role.
The St. Mary’s County State’s Attorney’s Office serves the residents of one of Southern Maryland’s key counties. With Mosier’s promotion, the office strengthens its leadership team as it handles a full docket of cases ranging from misdemeanors to serious felonies.
Sterling’s selection of Mosier for the deputy position underscores the importance of continuity and expertise in local prosecution. As the office faces ongoing challenges with violent crime and other priorities, experienced prosecutors like Mosier play a vital role in delivering justice for victims and the community.
Mosier’s commitment to training new attorneys and maintaining strong administrative policies will help ensure the office operates efficiently while upholding high standards in case handling and victim support.
The appointment is effective immediately, and Mosier will continue her active caseload alongside her new administrative responsibilities. Her leadership is expected to strengthen the office’s ability to address the most serious crimes in St. Mary’s County.
