"Heads roll" was an overly vindictive metaphor, because what actually happens is Skippy pays the poison victim some money, which rectifies the mistake, to some extent. So why would we ever spare them? By doing so, we're effectively shifting the burden to the victim. In delivering justice, consequences can't be eliminated, only redistributed.

And if the risk is really so small, then Skippy should have no problem assuming it. It's either them or little Timmy.