In the case of Brown v. United States in 1920, the Supreme Court ruled on a matter concerning self-defense and homicide. The defendant, Brown, had been convicted for murder after killing a man who was trespassing on his property with intent to harm him. He appealed this conviction arguing that he acted in self-defense and should not be held liable for protecting himself from imminent danger within his own home. The court agreed with Brown's argument stating that if a person is attacked in their own dwelling place or immediate surroundings where they have every right to be present, they are not obligated by law to retreat but may stand their ground and defend themselves against an attack even if it results in death of the attacker. This ruling established important precedent regarding laws related to self-defense.

In the dissenting opinion for Brown v. United States, Justice Oliver Wendell Holmes Jr. argued that a person should not be convicted of murder if they killed in self-defense while committing an illegal act, as long as the illegal act was not inherently dangerous or likely to provoke violence. He believed that the defendant's crime of smuggling alcohol did not justify his conviction for murder after he shot and killed a law enforcement officer who had discovered him during the commission of this non-violent crime. According to Holmes, it is unjustifiable to hold someone accountable for defending their life simply because they were engaged in an unrelated criminal activity at the time. This view contrasts with majority’s ruling which held that one forfeits their right to self-defense when engaged in unlawful activities.