The Commentaries had a particular influence in the United States; James Iredell, an original Associate Justice of the Supreme Court of the United States wrote that the Commentaries were "Books admirably calculated for a young Student, and indeed may instruct the most learned . . Pleasure and Instruction go hand in hand". When the Commentaries were first printed in North America, 1,400 copies were ordered for Philadelphia alone.[105] Academics have also noted the early reliance of the Supreme Court on the Commentaries, probably due to a lack of US legal tradition at that time.[106] Robert Ferguson notes that "all our formative documents – the Declaration of Independence, the Constitution, the Federalist Papers and the seminal decisions of the Supreme Court under John Marshall – were drafted by attorneys steeped in Sir William Blackstone's Commentaries on the Laws of England. So much was this the case that the Commentaries rank second only to the Bible as a literary and intellectual influence on the history of American institutions".[107] Even today, the Commentaries are cited in Supreme Court decisions between 10 and 12 times a year

Blackstone's Ratio:

Among the most well-known of Blackstone's contributions to judicial theory is his own statement of the principle that it "is better that ten guilty persons escape than that one innocent suffer".[114]

While this argument originates at least as far back as Genesis 18:23–32 in the Bible,[115][116] as well as versions by Maimonides[115][117][118] and Sir John Fortescue,[119] Blackstone's analysis is the one picked up by Benjamin Franklin[120] and others, so that the term has become known as "Blackstone's Ratio".[121]

As John Adams, having studied Blackstone,[122] put it:

“ It is more important that innocence should be protected, than it is, that guilt be punished; for guilt and crimes are so frequent in this world, that all of them cannot be punished.... when innocence itself, is brought to the bar and condemned, especially to die, the subject will exclaim, 'it is immaterial to me whether I behave well or ill, for virtue itself is no security.' And if such a sentiment as this were to take hold in the mind of the subject that would be the end of all security whatsoever.[123] ”

Blackstone's Ratio is a maxim of English law, having been established as such within a few decades of Blackstone's work being published.[124] It is also cited in courts and law in the US, and is strongly emphasised to American law students