Joan Cassidy Stetson, 53, a former lawyer for the Justice Department and a trustee of the Holton-Arms School for Girls in Bethesda, died of cancer Monday at Georgetown University Hospital. She lived in Bethesda.

Mrs. Stetson was born and reared in Bangor, Maine. She graduated from Georgetown University, where she later earned a master's degree in law, and earned a law degree from Boston College.

She then was a lawyer with the Justice Department for a short time before resigning to devote herself to her family.

Besides serving as a Holton-Arms trustee, Mrs. Stetson was a director of the International Student House in Washington. She was a member of the Four Seasons Garden Club and the Sulgrave Club.

Survivors include her husband, Edwin F., two sons, John E. and Stephen W., and a daughter, Sarah D., all of Bethesda; another daughter, Barbara Anne, of Portland, Maine; her mother, Isabel Delano Cassidy, a sister, Barbara Cassidy, and a brother, John Cassidy, all of Bangor, Maine, and another sister, Mrs. Raymond Flynn, of Kennebunk, Maine.

The family suggests that expressions of sympathy be in the form of contributions to the Holton-Arms School, the Madeira School, or to the Landon School.