The Presumption of Innocence

The presumption of innocence — being innocent until proven guilty — is a legal right that the accused has in Canada. It states that no person shall be considered guilty until finally convicted by a court. The burden of proof, beyond a reasonable doubt, is thus on the prosecution, which has to collect and present enough proving evidence to convince the judge and jury, who are restrained and ordered by law to consider only actual evidence and testimony that is legally admissable, and in most cases lawfully obtained, that the accused is guilty beyond a reasonable doubt. In case of remaining doubts, the accused is to be found not guilty ; this idea expressed by the Latin legal maxim "In dubio pro reo".

This duty on the prosecution was famously referred to as the 'golden thread' in the criminal law by Lord Sankey LC in Woolmington v DPP [1935] AC 462:

Throughout the web of the English criminal law one golden thread is always to be seen - that it is the duty of the prosecution to prove the prisoner's guilt subject to what I have already said as to the defence of insanity and subject also to any statutory exception...

In principle, the defense does not have to 'prove' anything. The defense may present evidence tending to show that there is a reasonable doubt as to the guilt of the accused.

In Canada, section 11(d) of the Canadian Charter of Rights and Freedoms states: "Any person charged with an offence has the right to be presumed innocent until proven guilty according to law in a fair and public hearing by an independent and impartial tribunal".

In criminal law, Blackstone's formulation (also known as Blackstone's ratio or the Blackstone ratio) is the principle: "better that ten guilty persons escape than that one innocent suffer", expressed by the English jurist William Blackstone in his Commentaries on the Laws of England, published in the 1760s.