Beyond a Reasonable Doubt
The standard of "beyond a reasonable doubt" (BARD) is a common law standard of proof in criminal matters. This standard is exclusively used in criminal or quasi-criminal proceedings. This includes not only adult criminal trials, but also young offender cases, adult sentencing, and certain provincial penal offences.
The standard of "reasonable doubt" consists of a doubt based on reason and common sense which must be logically based upon the evidence or lack of evidence. It is not based on "sympathy or prejudice". 
The standard as the ultimate burden of proof is "inextricably intertwined with that principle fundamental to all criminal trials, the presumption of innocence". The burden should never shift to the accused.
Level of Certainty
Proof beyond a reasonable doubt "it does not involve proof to an absolute certainty; it is not proof beyond any doubt nor is it an imaginary or frivolous doubt."
However, belief that the accused is "probably guilty" is not sufficient and must acquit.
The burden of proof placed upon the Crown lies “much closer to absolute certainty than to a balance of probabilities.” The standard is more "than proof that the accused is probably guilty" in which case the judge must acquit.
To know something with "absolute certainty" is to "know something beyond the possibility of any doubt whatsoever". 
Relationship to Evidence
“[A] reasonable doubt does not need to be based on the evidence; it may arise from an absence of evidence or a simple failure of the evidence to persuade the trier of fact to the requisite level of beyond reasonable doubt.”
The standard of BARD only applies to the evaluation of the evidence as a whole and not individual aspects of the evidence. The standard should be applied for the purpose of determining whether individual elements are proven beyond a reasonable doubt.
Inferences and Conjecture
Reasonable doubt must come as a rational conclusion from the evidence available and not as a basis of conjecture.
Risk of Wrongful Conviction
A verdict of guilt must be considered carefully in order to protect the liberty of the accused and protect against a wrongful conviction.
The standard should not be articulated in a way that would likely cause the standard to be applied subjectively.
Consequence of Reasonable Doubt
The finding of reasonable doubt "is not the same as deciding in any positive way that [the allegations] never happened." It is simply a finding that the evidence is not of "sufficient clarity" to allow an acceptance of the essential facts to an "acceptable degree of certainty or comfort" sufficient to displace the presumption of innocence.
- affirmed under the English common law of England in Woolmington v D.P.P.,  A.C. 462 at 481-82 (H.L.)
R v Lifchus, 1997 CanLII 319 (SCC),  3 SCR 320 at para 36
See also: In R v JMH, 2011 SCC 45 (CanLII) at para 39 ( “a reasonable doubt does not need to be based on the evidence; it may arise from an absence of evidence or a simple failure of the evidence to persuade the trier of fact to the requisite level of beyond reasonable doubt.”)
- Lifchus, supra at para 36
- Lifchus, supra at para 36
- Lifchus, supra, at para 31, 36
- Lifchus, supra at para 36
- R v Starr, 2000 SCC 40 (CanLII) at para 242
- Lifchus, supra at 36
- R v Layton, 2008 MBCA 118 (CanLII)
- R v JMH, supra
R v Stewart, 1976 CanLII 202,  2 SCR 748 at 759-61
R v Morin, 1988 CanLII 8,  2 SCR 345 at 354, 44 CCC (3d) 193
R v White, 1998 CanLII 789,  2 SCR 72, 125 CCC (3d) 385 at paras 38-41
R v McKay, 2017 SKCA 4 (CanLII) at para 18 ("The standard of proof, being beyond a reasonable doubt, is not to be applied to individual pieces of evidence. Rather, it is to be applied to the evidence as a whole for the purpose of determining whether each of the necessary elements of an offence has been established.")
- R v Wild 1970 CanLII 148 (SCC),  SCR 101 at 113
R v W(R), 1992 CanLII 56 (SCC),  2 SCR 122 in context of child witnesses ("Protecting the liberty of the accused and guarding against the injustice of the conviction of an innocent person require a solid foundation for a verdict of guilt")
R v Stubbs, 2013 ONCA 514 (CanLII) at para 99
R v Bisson, 1998 CanLII 810 (SCC),  1 SCR 306 at p. 311 (SCR)
R v Ghomeshi, 2016 ONCJ 155 (CanLII) at para 140
Ghomeshi, ibid. at para 140 and 141
Use of Illustrations in Articulating the Standard
Examples and illustrations are permissible in describing the standard of BARD as long as it does not takeaway the right to reach their own conclusions.
The use of illustrations or examples in articulating the standard of BARD is "fraught with difficulty". The use of examples tends to lower the standard to that of a balance of probabilities and encourage a subjective standard.
Raising a Doubt
A reasonable doubt cannot be based on "speculation or conjecture".
The Crown has no burden to "negativing every conjecture to which circumstantial evidence might be consistent with the innocence of the accused."
The absence of evidence due to the police's failure to take investigative steps will sometimes be an important consideration in whether the Crown has proven its case beyond a reasonable doubt.
The defence is permitted to elicit evidence from witnesses of potential inadequacies in the investigation. Oversights in investigation "can be particularly important where no defence evidence is called."
R v Henderson, 2012 NSCA 53 (CanLII) at para 40
R v White, 1994 CanLII 4004 (NS CA)
R v Eastgaard, 2011 ABCA 152 (CanLII) at para 22, aff’d 2012 SCC 11 (CanLII)
R v Tahirsylaj, 2015 BCCA 7 (CanLII) at para 39
R v Paul (1975), 1975 CanLII 185 (SCC), 27 CCC (2d) 1 (S.C.C.), at 6, (1975),  1 SCR 181, 64 D.L.R. (3d) 491 (S.C.C.)
R v Bero 2000 CanLII 16956 (ON CA), (2000), 151 CCC (3d) 545 (Ont.C.A.) at paras 56 to 58
R v Gyimah, 2010 ONSC 4055 (CanLII), at para 20