jaime caetano was reported to have been hospitalized and "in fear for [her] life" after an altercation with her "abusive" boyfriend. after obtaining several restraining orders that "proved futile", caetano accepted a stun gun from a friend for self-defense. one night, when her ex-boyfriend confronted her outside her work and threatened her, she displayed the stun gun and successfully avoided an altercation. however, when police discovered that she was in possession of the stun gun, she was arrested, tried, and convicted under a massachusetts law that outlawed the possession of stun guns. the massachusetts supreme judicial court had said her stun gun was "not the type of weapon that is eligible for second amendment protection” because it was “not in common use at the time of [the second amendment’s] enactment.” caetano then appealed the massachusetts court's ruling to the supreme court of the united states.