The case for saving the greater number
If every available option causes harm, choosing the action that prevents the most death or suffering may appear morally necessary.
Individuals are not interchangeable units
A person has interests, rights and a life of their own. Deliberately sacrificing them can treat them merely as a tool for others.
Doing harm differs from allowing harm
Some moral theories distinguish directly causing injury from failing to prevent an existing threat. The distinction is important but not always decisive.
Consent can change the judgement
A voluntary sacrifice differs from imposing death or injury upon an unwilling innocent person.
Certainty matters
Real decisions rarely guarantee that harming one person will save many. Speculative benefits provide weaker justification.
Responsibility matters
Harming the person who created the danger may differ from harming an unrelated innocent individual.
Rules protect against abuse
Allowing individuals to be sacrificed whenever authorities claim a greater good can justify severe injustice and manipulation.
Evidence notes
Assessment should examine necessity, certainty, consent, proportionality, alternatives, responsibility for the threat and safeguards against abuse.
Ethical questions
May an innocent person be deliberately used to save others?
How certain must the benefit be?
Would permitting the action create a rule that authorities could misuse?
Conclusion
Harming one person may sometimes be defensible when no less harmful option exists and the greater danger is immediate and certain. Deliberately sacrificing an innocent person, however, requires the strongest possible justification and strict limits.