Force which creates a substantial risk of causing death or serious bodily injury. Related Terms: Weapon, Self-Defence, Stand Your Ground, Curtilage, Semayne's Case, Se Defendendo. Deadly force is that force which is reasonably likely to cause death.. But in Smith v. City of Hemet, the same Court overruled itself and the Vera Crus definition as Justice Reinhardt presiding offered another standard for deadly force, as force which: