The standard of proof asks to how convinced the trier of fact must be of some something. Canadian criminal law has three core standards:
- Proof beyond a reasonable doubt which is the standard to be met by the Crown against the accused;
- a balance of probabilities or Proof on a preponderance of the evidence which is the burden of proof on the accused when he has to meet a presumption requiring him to establish or to prove a fact or an excuse;
- Evidence raising a reasonable doubt which is what is required to overcome any other presumption of fact or of law. Once a prima facie case has been established by the evidence of the crown, there is no need to prove innocence. Rather the accused need only raise a doubt in the evidence.
The US has a fourth standard known as "clear and convincing evidence" which is a middle ground between the two standards, however, this has never been officially adopted in Canada. When a proposition at issue in a case, such as an element of an offence, must be proven, the standard must be reached using the weight of the totality of evidence presented, not on each individual piece of evidence .
Balance of ProbabilitiesEdit
The "balance of probabilities" is described as being "more probable than not", or more technically, the chance of the proposition being true is more than 50%. This standard is known as the civil standard as it exclusively used in civil trial cases.
- Continental Insurance Co. v. Dalton Cartage Co., 1982 CanLII 13 (SCC),  1 SCR 164 - SCC rejected a variable standard, adopting only balance of probabilities
Beyond a Reasonable Doubt (BARD)Edit
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". 
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 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.
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.
“[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.
Reasonable doubt must come as a rational conclusion from the evidence available and not as a basis of conjecture.
Where the issue is the reliability or credibility of a witness, the courts must generally consider corroborative evidence.
- 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 S.C.R. 320 at para. 36
See also: In R. v. J.M.H., 2011 SCC 45 at 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, at para. 36
- Lifcus at para. 36
- Lifchus at para. 36
- Lifchus at para. 36
- R. v. Starr, 2000 SCC 40 at para 242
- Lifchus at 36
- R. v. J.M.H., 2011 SCC 45
- Stewart v. The Queen, 1976 CanLII 202,  2 S.C.R. 748 at 759-61
R. v. Morin, 1988 CanLII 8,  2 S.C.R. 345 at 354, 44 C.C.C. (3d) 193
R. v. White, 1998 CanLII 789,  2 S.C.R. 72, 125 C.C.C. (3d) 385 at paras. 38-41
- R. v. Wild 1970 CanLII 148 (SCC),  SCR 101 at 113
- R. v. Kehler, 2004 SCC 11,  1 S.C.R. 328 at paras. 12-23
Sufficiency of ProofEdit
Before any evidence gets to a trier of fact there is often a requirement to discharge an evidential burden for the trier of law (i.e. the judge).
In a preliminary inquiry the Crown must show on the whole that the evidence they will present is sufficient to potentially convict the accused. The purpose of this initial evaluation is to avoid frivolous suiting being brought in that have no chance at success.
The leading case for the standard of proof needed before evidence can be put to the jury is United States of America v. Shephard, 1976 CanLII 8 (SCC),  2 SCR 1067. The Court held that:
- [The] which governs a trial Judge in decideing whether the evidence is sufficient to justify him in withdrawing the case from the jury, and this is to be determined according to whether or not there is any evidence upon which a reasonable jury properly instructed could return a verdict of guilt.
In a case where some of the evidence the Crown is relying upon is not directly to the issue of the case, the Crown must satisfy the judge that "the evidnece, if believed, could reasonably support an inference of guilt."
- R.v. Arcuri, SCC 54 (CanLII),  2 SCR 828
Frequently seen standards of proof that are seen include:
- "air of reality" / prima facie case
- reasonable and probable grounds / reasonably-based probability
- reasonable suspicion
Air of Reality TestEdit
The air of reality test determines whether a particular legal defence should be consider by the trier-of-fact. When the standard is met, the effect is to add a burden upon the Crown to prove that the defence fails beyond a reasonable doubt.
In the context of a jury trial, the test determines whether the judge will give instructions to the jury that they should consider the particular defenses. .
The air of reality test creates a burden of evidence, not a persuasive burden.
The jury should be instructed of defences that have evidence supporting it. By inference, a judge "judge has a positive duty to keep from the jury defences lacking an evidential foundation". There must be evidence support each element of the defence.
The test requires that there must be "some evidence" upon which "a properly instructed jury acting reasonably could base an acquittal".
The decision of a judge on the air of reality test may be reviewed as a "question of law" on a standard of "correctness".
The judge must consider whether inferences would be necessary for the defence to succeed and whether those inferences from the evidence are reasonable.
- Cinous at para. 52 ("It is trite law that the air of reality test imposes a burden on the accused that is merely evidential, rather than persuasive.")
- R. v. Cinous, 2002 SCC 29 (CanLII),  2 S.C.R. 3 at para. 57 and 82
- R. v. Ribic, 2008 ONCA 790 at para. 38
- R. v. Ribic, at para. 38 (all defences "that are realistically available on the evidence")
Cinous, at para. 50 (“a defence should be put to a jury if and only if there is an evidential foundation for it”)
- R. v. Gunning, [2005 SCC 27 2005 SCC 27] (CanLII),  1 S.C.R. 627, at para. 29
- Ribic at para. 38 ("if evidential support for a necessary element of a defence is lacking, the air of reality test will not be met.")
- Cinous, at para. 83
- R. v. McRae 2005 CanLII 26592 (ON CA) at para. 38 ("[T]he question of whether there was an air of reality to the defence of duress is an issue of law")
Cinous at para. 55
R. v. Ryan, 2011 NSCA 30 (CanLII) at para. 114
- Cinous at para. 54
- Cinous at para. 54 ("whether the defence is likely, unlikely, somewhat likely, or very likely to succeed at the end of the day")
- Cinous at para. 65 and 83
R. v. Savoury 2005 CanLII 25884 (ON CA) at para. 45
R. v. Basit, 2013 BCSC 70 (CanLII) at para. 7