Presumption of innocence

The presumption of innocence is a legal principle that every person accused of any crime is considered innocent until proven guilty. Under the presumption of innocence, the legal burden of proof is thus on the prosecution, which must present compelling evidence to the trier of fact (a judge or a jury). If the prosecution does not prove the charges true, then the person is acquitted of the charges. The prosecution must in most cases prove that the accused is guilty beyond a reasonable doubt. If reasonable doubt remains, the accused must be acquitted. The opposite system is a presumption of guilt.
In many countries and under many legal systems, including common law and civil law systems (not to be confused with the other kind of civil law, which deals with non-criminal legal issues), the presumption of innocence is a legal right of the accused in a criminal trial. It is also an international human right under the UN's Universal Declaration of Human Rights, Article 11. 
In non-criminal proceedings (like breach of contract) the defendant is usually presumed correct unless the plaintiff presents a moderate level of evidence and thus switches the burden of proof to the defendant. However, there are exceptions to this.
History.
Roman law.
The sixth-century "Digest" of Justinian (22.3.2) provides, as a general rule of evidence: "Ei incumbit probatio qui dicit, non qui negat""Proof lies on him who asserts, not on him who denies". It is there attributed to the second and third century jurist Paul. It was introduced in Roman criminal law by emperor Antoninus Pius.
A civil law system is a modern legal system derived from the ancient Roman legal system (as opposed to the English common law system). The maxim and its equivalents have been adopted by many countries that use a civil law system, including Brazil, China, France, Italy, Philippines, Poland, Romania and Spain.
In the criminal law system of Hungary, "it is the most general concept that everybody (suspect, accused, or not) must be considered innocent until a final judgement finds the person guilty. But there is another point of view also,—and it usually appears in the international declarations—which does not connect the stopping of the presumption of innocence to a final judgement, but it is 'satisfied' with any provision that states guilt, that is based on law. There is a significant difference between the two formulations. The final judgement usually means the end of the punitive procedure, which can take place many more years after the time of the crime committed. It can happen, for instance, in the case of caught in the act, the statements of witnesses, the confession of the offender, the perpetrator must be presumed innocent for some years till the final judgement is reached despite the above enlisted facts".
Talmudical law.
According to Talmud, "every man is innocent until proved guilty. Hence, the infliction of unusual rigours on the accused must be delayed until his innocence has been successfully challenged. Thus, in the early stages of the trial, arguments in his defence are as elaborate as with any other man on trial. Only when his guilt has become apparent were the solicitous provisions that had been made to protect defendants waived".
Islamic law.
Similar to that of Roman law, Islamic law also holds the principle that the onus of proof is on the accuser or claimant based on a hadith documented by Imam Nawawi. "Suspicion" is also highly condemned, this also from a hadith documented by Imam Nawawi as well as Imam Bukhari and Imam Muslim.
After the time of Muhammad, the fourth Caliph Ali ibn Abi Thalib has also been cited to say, "Avert the prescribed punishment by rejecting doubtful evidence."
Middle Ages in Europe.
Western Europe.
After the collapse of the Western Roman Empire, the West began to practice feudal law, which was a synthesis of aspects of Roman law as well as some Germanic customs according to the new elite, including presumed guilt. For instance, the accused could prove his innocence by having twelve people swear that he could not have done what he was accused of. In practice, this tended to favor the nobility over the lower classes, whose witnesses risked being seen as less credible. After the rediscovery of Roman law in the 12th century and the development of the "jus commune", the canon law of the Catholic Church influenced the common law during the medieval period through its preservation of Roman law doctrine of the presumption of innocence.
Eastern Europe.
Following the aforementioned Roman law of Justinian, who lived at the dawn of the medieval era, the Byzantine Empire generally continued along his legal code which includes presumption of innocence. This also influenced nearby states within its cultural sphere, such as Orthodox, Slavic principalities like Serbia.
Meaning.
"Presumption of innocence" serves to emphasize that the prosecution has the obligation to prove each element of the offense beyond a reasonable doubt (or some other level of proof depending on the criminal justice system) and that the accused bears no burden of proof. This is often expressed in the phrase "presumed innocent until proven guilty", coined by the British barrister Sir William Garrow (1760–1840) during a 1791 trial at the Old Bailey. Garrow insisted that accusers be robustly tested in court. An objective observer in the position of the juror must reasonably conclude that the defendant almost certainly committed the crime. In 1935, in its judgment of "Woolmington v Director of Public Prosecutions", the English Court of Appeal would later describe Garrow's articulation as being the 'golden thread' connecting both the criminal burden of proof and the presumption of innocence within the web of English criminal law.
The presumption of innocence was originally expressed by the French cardinal and canonical jurist Jean Lemoine in the phrase ""item quilbet presumitur innocens nisi probetur nocens" (a person is presumed innocent until proven guilty)", based on the legal inference that most people are not criminals. However, this referred not merely to the fact that the burden of proof rests on the prosecution in a criminal case, but the protections which a defendant should be given: prior notice of the accusation being made against them, the right of confrontation, right to counsel, etc. It is literally considered favorable evidence for the accused that automatically attaches at trial. It requires that the trier of fact, be it a juror or judge, begin with the presumption that the state is unable to support its assertion. To ensure this legal protection is maintained, a set of three related rules govern the procedure of criminal trials. The presumption means:
Blackstone's ratio as expressed by the English jurist William Blackstone in his seminal work, "Commentaries on the Laws of England", published in the 1760s, said that:
The idea subsequently became a staple of legal thinking in Anglo-Saxon jurisdictions and continues to be a topic of debate.
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":
The fundamental right.
This right is considered important enough in modern democracies, constitutional monarchies and republics that many have explicitly included it in their legal codes and constitutions:
Modern practices.
United Kingdom.
In the United Kingdom changes have been made affecting this principle. Defendants' previous convictions may in certain circumstances be revealed to juries. Although the suspect is not compelled to answer questions after formal arrest, failure to give information may now be prejudicial at trial. Statute law also exists which provides for criminal penalties for failing to decrypt data on request from the police. If the suspect is unwilling to do so, it is an offence. Citizens can therefore be convicted and imprisoned without any evidence that the encrypted material was unlawful. Furthermore, in sexual offence cases such as rape, where the sexual act has already been proved beyond reasonable doubt, there are a limited number of circumstances where the defendant has an obligation to adduce evidence that the complainant consented to the sexual act, or that the defendant reasonably believed that the complainant was consenting. These circumstances include, for example, where the complainant was unconscious, unlawfully detained, or subjected to violence.
Canada.
In Canadian law, the presumption of innocence has been reinforced in certain instances. The "Criminal Code" previously contained numerous provisions according to which defences to certain offences were subject to a reverse onus: that is, if an accused wishes to make that defence, they had to prove the facts of the defence to a balance of probabilities, rather than the Crown having to disprove the defence beyond a reasonable doubt. This meant that an accused in some circumstances might be convicted even if a reasonable doubt existed about their guilt. In several cases, various reverse onus provisions were found to violate the presumption of innocence provision of the Charter of Rights and Freedoms. They were replaced with procedures in which the accused merely had to demonstrate an "air of reality" to the proposed defence, following which the burden shifted to the Crown to disprove the defence.
Bill C-51, "An Act to amend the Criminal Code and the Department of Justice Act and to make consequential amendments to another Act", received Royal Assent in December 2018. Among other things, it eliminated several reverse onus provisions from the "Criminal Code", some of which had previously been found unconstitutional, and others pre-emptively in order to avoid further "Charter" challenges.