Chief Justice Shaw of the Massachusetts Supreme Court made this observation in 1850 about the reasonable standard of doubt: the cornerstone of American criminal justice is that the accused is presumed innocent until proven guilt beyond a doubt.   The U.S. Supreme Court has held that “the due process clause protects the defendant from conviction unless there is unequivocal evidence of any fact necessary to support the accused crime.”  The U.S. Supreme Court first discussed the term in Miles v. U.S.: “The evidence on the basis of which a jury is authorized to render a guilty verdict must be sufficient to warrant a conviction, to the exclusion of a reasonable doubt.”  The U.S. Supreme Court has extended the reasonable standard of doubt to juvenile trials because they are considered quasi-criminal.  “We expressly believe that the due process clause protects the defendant from conviction, unless there is unequivocal evidence of any fact necessary to present the crime of which he is accused.”  In Canada, the phrase “beyond a reasonable doubt” needs to be clarified in favour of the jury.   The main decision is R. v. Lifchus, where the Supreme Court discussed to the jury the good elements of an indictment on the notion of “reasonable doubt” and stated that “the correct explanation of the required burden of proof is essential to ensure a fair criminal trial.” While the Court did not prescribe specific language that a trial judge must use to explain the concept, it recommended that certain elements be included in a jury indictment and highlighted comments that should be avoided.
“What is a reasonable doubt? It is a term that is often used, probably quite well understood, but not easy to define. This is not a mere doubt; Because everything that relates to human affairs, and according to moral evidence, is open to possible or imaginary doubts. It is this state of the case that, after all the settlement and examination of all the evidence, leaves the minds of the jurors in the state that they cannot say that they feel a lasting conviction of the truth of the indictment to a moral certainty. The burden of proof lies with the Public Prosecutor`s Office. All legal presumptions independent of evidence speak of innocence; and every human being is considered innocent until proven guilty. If justified doubts remain after such evidence, the defendant is entitled to an acquittal. For it is not sufficient to establish a probability, even if it results from the doctrine of chance, that the alleged fact is true rather than the opposite; but the evidence must prove the truth of the fact with reasonable and moral certainty; A certainty that convinces and guides the understanding and satisfaction of reason and judgment of those who are compelled to act conscientiously accordingly. We see this as unequivocal evidence.  Beyond a reasonable doubt, a legal standard of proof is required to confirm a criminal conviction in most adversarial legal systems.  This is a higher standard of proof than the balance of risk (commonly used in civil matters) and is therefore generally reserved for criminal cases where what is at stake (e.g., a person`s liberty) is considered more serious and therefore merits a higher threshold.
A man is on trial for murder. His fate is in the hands of twelve jurors, chosen by a judge and charged with granting the accused the presumption of innocence. It is up to the prosecutor to prove guilt beyond any doubt. “[A reasonable doubt] is a doubt that is based on a truly tangible substantial basis, not on mere whims and conjectures. It must be such doubts that would give rise to a serious uncertainty that is caused in your mind for reasons of unsatisfactory nature of the evidence or its absence. A reasonable doubt is not just a possible doubt. That is a really considerable doubt. This is a doubt that a reasonable man can seriously entertain. What is needed is not absolute or mathematical certainty, but moral certainty.
“Jurors are always told that if there is to be a conviction, the prosecution must prove the case without a doubt. This statement can only mean that in order to be acquitted, the prisoner must “satisfy” the jury. It is the law as it is in the Court of Criminal Appeal in Rex v. Davies 29 times LR 350; 8 Cr App R 211, the guiding principle of which rightly states that, in cases where intent forms part of a criminal offence, the defendant is not required to prove that the alleged act was accidental.