This statement draws on the earlier statement of Sir John Fortescue, De Laudibus Legum Angliae (c. 1470), who wrote that "one would much rather that twenty guilty persons should escape the punishment of death, than that one innocent person should be condemned and suffer capitally."
This legal theory has been designated "Blackstone's Formulation" after Sir William Blackstone, who wrote in his famous Commentaries on the Laws of England (1765-1769), it is "better that ten guilty persons escape than that one innocent suffer." This maxim was opposed by William Paley and defended by Samuel Romilly. Others have embraced this principle as well. Voltaire wrote in Zadig (1747) that "Il vaut mieux hasarder de sauver un coupable que de condamner un innocent" ("It is better to risk sparing a guilty person than to condemn an innocent one"). Benjamin Franklin later wrote in 1785 (Works, p. 293) "it is better [that one hundred] guilty Persons should escape than that one innocent Person should suffer." The theory that it is better to err by letting the guilty live or go free than to punish the innocent has since become part of the bedrock of American common law.
In dictatorial fashion, however, Otto von Bismarck is quoted as saying "it is better that ten innocent men suffer than one guilty man escape" (John W. Wade, Uniform Comparative Fault Act, 14 Forum 379, 385 (1979), and Pol Pot said, "You can arrest someone by mistake; never release him by mistake."..."Better to kill an innocent by mistake than spare an enemy by mistake." (Henri Locard, Pol Pot's Little Red Book: The Sayings of Angkar, pp. 208-209). Other statists have uttered similar sentiments.
But the principle articulated by Blackstone, Mather and others is derived from Abraham's famous statement to God in Gen. 18.23-26:
And Abraham drew near, and said, Wilt thou also destroy the righteous with the wicked? Peradventure there be fifty righteous within the city: wilt thou also destroy and not spare the place for the fifty righteous that are therein? That be far from thee to do after this manner, to slay the righteous with the wicked: and that the righteous should be as the wicked, that be far from thee: Shall not the Judge of all the earth do right? And the LORD said, If I find in Sodom fifty righteous within the city, then I will spare all the place for their sakes.
It was during the Albigensian Crusade at the massacre of Albigensians or Cathars (proto-Protestants) at Béziers, France, in July 1209, almost exactly 800 years ago, that Abbot Arnold Amalric is said to have uttered the infamous phrase, "Caedite eos. Novit enim Dominus qui sunt eius" ("Kill them. For the Lord knows those who are his, or, Kill them all, let God sort them out"). Although justice is imperfect here on earth, magistrates do better to follow the example set by our Lord and expressed by his servant Abraham, by sparing the wicked lest the innocent perish.