Function could_have_prevented 

pub fn could_have_prevented(
    had_ability: bool,
    had_opportunity: bool,
    did_act: bool,
) -> bool

Counterfactual omission (“could have prevented X but did not”): the agent had the ability and the opportunity to bring about the prevention, yet did not act. The counterfactual that turns a bare omission into a culpable one.