Blackstone's ratio

In criminal law, Blackstone's ratio is the ratio between letting guilty go unpunished (error of impunity) and convicting innocent people, two forms of miscarriage of justice.

Version

v1 · 2026-09-28 · History

Domain-specific #

8219

Domain group

Professional & Organizational Practice

Origin domain

Law & Governance

Subdomains

Criminal Law, Criminal Justice → Law & Governance

Core Idea

Blackstone's ratio is treated here as the recurring criminal justice identity summarized by this source-grounded definition: In criminal law, Blackstone's ratio is the ratio between letting guilty go unpunished (error of impunity) and convicting innocent people, two forms of miscarriage of justice. In criminal law, Blackstone's ratio is the ratio between letting guilty go unpunished (error of impunity) and convicting innocent people, two forms of miscarriage of justice. There is also a long history of similar sentiments going back centuries in a variety of legal traditions.

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Better Free Than Wrongly Punished

When a judge decides whether someone did something wrong, they can make two kinds of mistakes: letting someone who did it go free, or punishing someone who didn't. Blackstone's ratio is the idea that punishing an innocent person is much worse, so it is better to let several guilty people go than to punish one innocent person.

The Two Mistakes Rule

In courts, two kinds of mistakes can happen: a guilty person goes free, or an innocent person gets punished. Both are unfair, but many people believe punishing the innocent is worse. Blackstone's ratio compares these two mistakes and says how many guilty people escaping is worth avoiding one innocent person being punished. People have said this with different numbers; Benjamin Franklin said it was better for 100 guilty people to escape than for one innocent person to suffer. Similar ideas show up in many older legal traditions, and people still argue about the right number today.

Weighing Two Kinds of Justice Errors

Blackstone's ratio, in criminal law, is the ratio between two kinds of miscarriage of justice: letting guilty people go unpunished (the error of impunity) and convicting innocent people. It expresses the principle that it is better for some number of guilty people to escape than for one innocent person to be punished, which tilts the system toward avoiding wrongful convictions. Similar sentiments appear centuries back in various legal traditions; for example, Al-Tirmidhi reports Muhammad saying a judge should err toward leniency when in doubt, and Benjamin Franklin gave the ratio as 100 to 1. The idea became a staple of legal thinking in systems descended from English criminal law. The exact number is still debated, and U.S. state high courts have adopted different values.

 

Blackstone's ratio expresses, in criminal law, the relative weight a justice system assigns to two kinds of miscarriage of justice: false acquittal of the guilty (the error of impunity) and wrongful conviction of the innocent. It asserts that wrongful conviction is worse, so it is preferable that some number of guilty people go free rather than one innocent person be punished. The ratio is not fixed; the number is a normative choice. Benjamin Franklin stated it as 100 to 1, and state high courts in the United States continue to adopt different numerical values. Comparable sentiments appear across legal traditions over centuries, including a saying Al-Tirmidhi attributes to Muhammad urging judges to avoid punishment where there is doubt and to err toward leniency. The idea became a staple of legal thinking in jurisdictions descended from English criminal law, and its exact calibration remains contested.

Scope of Application

• Evolving significance over time. From a mathematical point of view, the Ratio is methodologically flawed, and once the Ratio lost its claim to the authority of mathematics, its usefulness declined.

• Historic expressions of the principle. Maimonides argued that executing an accused criminal on anything less than absolute certainty would progressively lead to convictions merely "according to the judge's caprice" and was expounding on both Exodus.

• Historic expressions of the principle. Even Voltaire in 1748 in the work of Zadig used a similar saying, although in French his thought is stated differently than in the English translation: "It is from him that.

• By Blackstone. The Blackstone's formulation, stated by the English jurist William Blackstone in his seminal work Commentaries on the Laws of England in the 1760s, is.

• By Blackstone. The phrase, repeated widely and usually in isolation, comes from a longer passage, the fourth in a series of five discussions of rules of presumption by Blackstone.

Clarity

A clear use of Blackstone's ratio names the carrier, the operative relation, and the conditions under which the source treats the identity as present. The minimal definition is In criminal law, Blackstone's ratio is the ratio between letting guilty go unpunished (error of impunity) and convicting innocent people, two forms of miscarriage of justice.

Manages Complexity

Blackstone's ratio compresses multiple criminal justice details into a stable diagnostic relation. The source shows both the central mechanism—the phrase, repeated widely and usually in isolation, comes from a longer passage, the fourth in a series of five discussions of rules of presumption by Blackstone.—and the practical consequence—cullerne Bown has argued that both the rise and fall in significance of the Ratio can be explained by the.

Abstract Reasoning

1. Type the carrier. Identify the criminal justice entities to which the claim applies.
2. State the relation. Use the source-grounded identity: In criminal law, Blackstone's ratio is the ratio between letting guilty go unpunished (error of impunity) and convicting innocent people, two forms of miscarriage of justice.
3. Check operation and conditions. The phrase was absorbed by the British legal system, becoming a maxim by the early 19^th century.
4. Demand recognition evidence.

Knowledge Transfer

Within the home domain. Knowledge about Blackstone's ratio transfers literally when a new case preserves the same carrier type, relation, and recognition test. From a mathematical point of view, the Ratio is methodologically flawed, and once the Ratio lost its claim to the authority of mathematics, its usefulness declined. Maimonides argued that executing an accused criminal on anything less than absolute certainty would progressively lead to convictions merely "according to the judge's caprice" and was expounding on both Exodus 23:7 ("do not.

Neighborhood in Abstraction Space

Blackstone's ratio sits in a moderately populated region (48^th percentile for distinctiveness): it has near-neighbors but no dense thicket of look-alikes.

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Nearest neighbors

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• Skepticism in law — 0.86
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• Exploratory thought — 0.86

Computed from structural-signature embeddings · 2026-10-08