Beyond reasonable doubt is the standard of evidence required to validate a criminal conviction in most adversarial legal systems.
Generally the prosecution bears the burden of proof and is required to prove their version of events to this standard. This means that the proposition being presented by the prosecution must be proven to the extent that there could be no "reasonable doubt" in the mind of a "reasonable person" that the defendant is guilty. There can still be a doubt, but only to the extent that it would not affect a reasonable person's belief regarding whether or not the defendant is guilty. "The shadow of a doubt" is sometimes used interchangeably with reasonable doubt, but this extends beyond the latter, to the extent that it may be considered an impossible standard. Reasonable doubt is therefore used.
If doubt does affect a "reasonable person's" belief that the defendant is guilty, the jury is not satisfied beyond "reasonable doubt". The precise meaning of words such as "reasonable" and "doubt" are usually defined within jurisprudence of the applicable country.
Famous quotes containing the words reasonable and/or doubt:
“We criticize a thinker more acutely when he advances a proposition that is disagreeable to us; and yet it would be more reasonable to do so when his proposition is agreeable to us.”
—Friedrich Nietzsche (1844–1900)
“I have no doubt that it is a part of the destiny of the human race, in its gradual improvement, to leave off eating animals, as surely as the savage tribes have left off eating each other when they came in contact with the more civilized.”
—Henry David Thoreau (1817–1862)