So, Blackstone's law states that 1 innocent man going to jail is worse than 10 guilty men being set free. This principle seems to be a fundamental principle for all Western governments.

I'm wondering if this principle has been thoroughly analyzed though? It seems to be a byproduct of Christianity, and isn't it possible that the price society is paying (not being harsh enough on the accused) outweighs the benefits gained ?

Have enough people questioned this principle and done empirical analysis to see if it's a net positive to society?

Also, if we stop using Blackstone's principle and solely view 1 innocent man going to jail to be as bad as 1 guilty man set free, is that compatible with the presumption of innocence?

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    The "ratio" : ten vs one, is not very relevant.It is a regulative principle : government and the courts must err on the side of innocence. Dec 6, 2018 at 13:01
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    Its ground is ethical; see also Historic expressions of the principle with ref to Biblical source. Dec 6, 2018 at 13:03
  • @MauroALLEGRANZA Agreed. I'm mainly just talking about erring on the side of innocence. So, the view that 1 innocent man getting jailed is worst than 1 guilty man getting set free. I'm questioning why these two scenarios aren't viewed as equally bad. Dec 6, 2018 at 13:03
  • In all political and legal matters there is always a balancing act between the interest of the individual vs. the interest of society. Western democracies tend to lean towards individual rights. With that in mind weigh the enormous violation of an innocent individual's interest if jailed, against the marginal violation of societal interest should one (or ten) criminals go free.
    – christo183
    Dec 6, 2018 at 14:07
  • It seems to me that there's a necessity to the presumption of innocence, because the domain of possible false accusations is infinite. Kind of a game-theoretic proof. Dec 6, 2018 at 19:32

3 Answers 3


jack klompus, welcome to PSE.


The principle is foreshadowed rather in Judaism than Christianity : Genesis 18:32 for example.

The statement "I will not destroy it [Sodom] for ten's sake," Genesis 18:32 ... implies "better P- 10 guilty men escape than ten righteous men be killed," or, dividing both quantities by 10, "better (P- 10) / 10 guilty men escape than one righteous man be killed." Alexander Volokh, 'n Guilty Men', University of Pennsylvania Law Review, Vol. 146, No. 1 (Nov., 1997), pp. 173-216: 177.)

Volokh traces the principle, or prefigurations of it, in scholarly detail via the Ancient Greeks and Romans as well as the Torah.


"[B]etter that ten guilty persons escape, than that one innocent suffer," said English jurist William Blackstone. The ratio 10:1 has be- come known as the "Blackstone ratio." Lawyers "are indoctrinated" with it "early in law school." "Schoolboys are taught" it. In the fantasies of legal academics, jurors think about Blackstone routinely.

But why ten? Other eminent legal authorities through the ages have put their weight behind other numbers. "One" has appeared on Geraldo."'It's better for four guilty men to go free than one innocent man to be imprisoned,"' says basketball coach George Raveling. However, " [i] t's better to turn five guilty men loose than it is to convict one innocent one," according to Mississippi's former state executioner, roadside fruit stand operator Thomas Berry Bruce, who ought to know. "[I]t is better to let nine guilty men free than to convict one innocent man," counters Madison, Wisconsin, lawyer Bruce Rosen."' Justice Benjamin Cardozo certainly believed in five for execution,' and allegedly favored ten for imprisonment, which is a bit counter-intuitive. Benjamin Franklin thought "[t]hat it is better a hundred guilty persons should escape than one innocent person should suffer." Mario Puzo's Don Clericuzio heard about letting a hundred guilty men go free and, "[s]truck almost dumb by the beauty of the concept . .. became an ardent patriot."'' Denver radio talk show host Mike Rosen claims to have heard it argued "in the abstract, that it's better that 1000 guilty men go free than one innocent man be imprisoned," and says of the American judicial system, "Well, we got our wish."'

Or, perhaps, the recommended number of guilty men should be merely "a few," "some,", "several," "many" (particularly, more than eight), "a considerable amount,"20 or even "a goodly number."2'

Not all commentators weigh the importance of acquitting the guilty against the value of the conviction of one innocent man. A Georgia circuit court held in 1877 that it was "better that some guilty ones should escape than that many innocent persons should be subjected to the expense and disgrace attendant upon being arrested upon a criminal charge." Moreover, in Judge Henry J. Friendly's opinion, "most Americans would agree it is better to allow a considerable number of guilty persons to go free than to convict any appreciable number of innocent men." It is unclear whether a "considerable" number is greater or less than an "appreciable" one. (Volokh: 174-7.)


It appears to be a part of ordinary (Western) moral thinking that it is worse to let a guilty person go free than to cause suffering to an innocent person. It is not clear, to me at least, on exactly what moral principle this relies. I do not quarrel with the principle; I am simply not clear what it is and on what basis it rests.

Blackstone's principle involves a falsely precise metric. It is not possible to calculate, out of all context, how many of the guilty should go unpunished rather than one innocent person should suffer. Admirable sentiment as the principle may be, it is moral rhetoric rather than moral logic.

  • "I do not quarrel with the principle; I am simply not clear what it is and on what basis it rests." - It looks pretty deontological to me, particularly when you consider all the different numbers offered (i.e. the numbers are just placeholders and carry no actual meaning - it's about the principle rather than any precise numerical rule). If so, then trying to balance the scales of societal benefit, as OP would have us do, is a fruitless endeavor.
    – Kevin
    Mar 11, 2019 at 4:44

It's an Anglo-Saxon thing derived from English common law, so it's not obviously relevant in other parts of the West, continental Europe for example, though it's not unknown there.

Then it's true that something like Blackstone's Ratio has been around in Europe for a long time, but I'm not sure how useful the ancient history is. Once Blackstone used it, it took off in a big way. So some kind of answer is needed to the question of why it became so important then.

I don't think it has much to do with Christianity. The function of the dictum is to legitimise various policies in the criminal justice system which are highly consequential in terms of who is convicted and who is acquitted. Prior to Blackstone, Christianity had an alternative and highly developed approach to this, exemplified by the idea of a half-proof and most maturely expressed in the teachings of Baldus - see Franklin.

It has been used historically like a passage from the Bible, as something that supplies justification rather than something that seeks justification, as you would have it do. This started with Blackstone himself, who provided no argument to support the principle.

It is very hard to say how central the idea is today. Historically, it has been and many policies were justified explicitly by recourse to the principle. But today the policies are largely entrenched and all sorts of justifications are offered for them. A kind of scholarly crucible for this discussion is the question of the standard of proof - "beyond reasonable doubt" or "beyond any doubt" or "on the balance of probabilities" etc. Here ambition in the philosophy of law is largely limited to the ahistorical goal of justifying the existing arrangements, and even this remains elusive - see Picinali.

It is certainly possible to argue that the price society is paying (not being harsh enough on the accused) outweighs the benefits gained. For about 15 years Larry Laudan in the United States has been trying to make this argument, partly through the use of empirical evidence.

The presumption of innocence is a bit like Blackstone's Ratio in that it is not a policy in itself; rather it is a principle that can be used to justify a policy, such as excluding a certain kind of evidence. So compatibility per se is not really an issue in my view.

I think the best starting point for thinking about Blackstone's Ratio is to note that it assumes an objective frame of reference in which defendants are truly innocent or guilty and the court may get its verdict right or wrong. The dictum then seems to express a valid value judgement that ought to be consequential and in this way I think Blackstone promised a basis for policies that seemed quantitative, objective and democratic – in a word, modern. No wonder it was popular.

But Blackstone failed explain how to make the value judgement consequential. It isn’t clear how one gets from the ratio of 10:1 to any particular policy, as opposed to one slightly stronger or weaker, or indeed much stronger or weaker. Equally, it isn’t clear what policy options and practical consequences we should be comparing if you advocate 10:1 and I advocate 100:1. There is a methodological gap. Thus Blackstone’s Ratio left the law in an awkward state, half in and half out of modernity. Subsequent generations have been unable to fix the problem and gradually the lack of a cogent argument has I think caught up with the dictum, which has become less central.

You can find more about this, including my attempt to fix the methodological gap at Blackstone's Ratio Revisited.


[I]f we... solely view 1 innocent man going to jail to be as bad as 1 guilty man set free, is that compatible with the presumption of innocence?

A word about the analysis of this question. Blackstone’s principle and the presumption of innocence enter the analysis at two different places.

The presumption of innocence in law serves the same purpose as the null hypothesis in science. This principle applies at the beginning of the case. Assumed: the defendant’s actions are indistinguishable from those of the general population. Innocent until proven guilty - why?

After the facts are before the court, what standard is used to convict? This point is where Blackstone enters. The principle is expressed as the minimum acceptable ratio of false negatives (guilty go free) to false positives (innocent found guilty).

The principle corresponds to statistical significance in science. Significance is expressed as the probability that a given result occurred by random chance, such as 0.001 (1 in 1,000).

Assume the Blackstone ratio approaches 1.0; i.e., one innocent man going to jail is acceptable to avoid one guilty man being set free. Now the presumption of innocence is effectively worth less. At lower ratios, an arrest is more likely to result in a conviction on the same evidence than when a higher ratio is used.

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