Just come across this when looking for something else. While the justification of torture is jarring, the rest is unfortunately all-too-relevant.
The question is whether there are grounds for capital punishment if two witnesses are brought forward against a defendant, witnesses which in a civil case would be considered sufficiently trustworthy to warrant a conviction even though the defendant may firmly deny that he committed the crime.
I believe it to be against the custom and the rule of law, and in such a case the defendant should, depending on the circumstances, only be subjected either to temporal punishment or to torture in order to obtain a confession, and through a lucid and consistent confession a greater light may be obtained, by which the defendant can be so much the more safely convicted…
… more certainty will be required to impose capital punishment than to order a fine, for it is better (aside from a case of public danger) that the guilty be absolved than the innocent be condemned, and surely the word of two witnesses in a matter of such importance is very unreliable, for what is easier than that two men should conspire to defraud a single person, especially since perjuries and witnesses procured by money are today too widespread…
But if this evidence is lacking, then I think it is important for the tranquility of our conscience that nothing be pronounced about a man’s life… For the life of a man is a thing of such great value to God that the power over it which we obtain in this life can only be excused by a certain necessity.
But I think the goal of torture is not so much to obtain a bare confession as to obtain a new light from the circumstances of the confession and, through this opportunity, leading steadily to a calm, lucid and free confession through a spontaneous ratification of a confession made under torture, so that we may judge about his capital punishment with a greater peace of mind.
Leibniz, “On the death penalty (after 10 July 1697)” in The Shorter Leibniz Texts, edited and translated by Lloyd Strickland, London: Continuum, 2006, pp. 152-154.
Also worth checking out Strickland’s Leibniz Translations website which includes some other political pieces.