He served as Deputy District Attorney of the City and County of San Francisco for a short period. In 1882, he teamed up with A. A. Sargent, a former Minister to Germany and a former United States Senator. This partnership lasted until Sargent's death in 1887.
One of his most notable cases was The People vs. Tarm Poy, a case of hatchet murder in Chinatown. Stone represented the family of the deceased and manoeuvred his way through a net of complexly woven circumstantial evidence to gain a conviction. In gratitude, the Fong family solicited contributions from its members throughout California and presented Stone with a solitaire diamond as well as his fees.