In dubio pro reo

The rule of lenity is the doctrine that ambiguity should be resolved in favour of the more lenient punishment.

[3] To resolve all doubts in favour of the accused is in consonance with the principle of presumption of innocence.

[3] The main principle in the sentence was part of Aristotle's interpretation of the law and shaped the Roman law: Favorabiliores rei potius quam actores habentur (Digest of Justinian I, D.50.17.125),[4] meaning "The condition of the defendant is to be favored rather than that of the plaintiff.

In German law, the principle is not codified but has constitutional status and is derived from Article 103(2) of the Basic Law, Article 6 of the ECHR, and Section 261 of the Code of Criminal Procedure.

The common use of the phrase in the German legal tradition was documented in 1631 by Friedrich Spee von Langenfeld.