Especially when the victim is unarmed and laying on the floor and those who might choose to interfere were also unarmed.
You'll have to check the law books of the time. I do know that there was a duel on the Marlboro Pike just outside of Washington in Maryland between two congressmen in 1838.
I did. Dueling was a state issue and by 1857 had been outlawed in every Northern state but was still legal in almost every southern one. However, D.C. was under federal law and it had been it had been outlawed, some say because George Washington had been so opposed to the practice.
May I ask you for a source?