Reasonable doubt
Etymology
The phrase “beyond reasonable doubt” crystallized in English common law in the late 18th century. It does not demand absolute certainty — an impossible standard — but rules out doubt for which a reasonable person could give a reason, reflecting the principle that it is better that many guilty go free than one innocent be condemned.
noun phrase · /REE-zuh-nuh-bul dowt/
The standard of proof in a criminal trial, requiring guilt to be so well established that no sensible person would question it.
What it names
The deliberately high bar for a conviction, tilting the system toward freeing the guilty over jailing the innocent.
Example
The jury believed he probably did it, but “probably” is not beyond reasonable doubt, so they acquitted.
Related idea
Reasonable doubt is the demanding criminal standard; civil cases use the far lower preponderance of the evidence, meaning merely more likely than not — which is why the same act can lose a lawsuit yet not a prosecution.