Philippa Foot is most known for her invention of the Trolley Problem thought experiment in the 1960s. A lesser known variation of hers is as follows:
Suppose that a judge is faced with rioters demanding that a culprit be found for a certain crime. The rioters are threatening to take bloody revenge on a particular section of the community. The real culprit being unknown, the judge sees himself as able to prevent the bloodshed from the riots only by framing some innocent person and having them executed.
These are the only two options: execute an innocent person for a crime they did not commit, or let people riot in the streets knowing that people will die. If you were the judge, what would you do?
I agree also by rules-based utilitarianism. It's important not just to consider the immediate, short-term utilitarian outcome, but to consider the utility of a world whereby we regularly make the same type of decision.
In a world where a riot is all it takes to sentence unpopular people to death, you create a perverse incentive for people to riot -- or threaten to riot -- in order to pervert the proper carriage of justice. Who knows how much net harm would be done in this world ruled by mob justice.
But the alternative is a world where rule of law exists, which I think is a far better world to live in.