Evidence provides a means of allowing facts to be proved for the purpose of deciding issues in litigation. Only evidence that is admissible, material and relevant can be considered. Even then evidence can often have the side-effect of creating prejudice, and if the prejudicial effect is more significant than the probative value, it might be ruled inadmissible for that reason.
For a trier-of-fact to receive evidence, the judge must be satisfied that the evidence is:
- not barred by rules of admissibly, and
- not subject to discretionary exclusion.
Once relevance and materiality is established the remaining steps tend to reduce the scope of admissibility by excluding evidence.
- R. v. Candir, 2009 ONCA 915 , per Watt J.A. at para 46 - requires evidence be (1) relevant (2) material (3) admissible
R. v. Cyr, 2012 ONCA 919 (CanLII) at para. 96 - sets out the four points of admissibility
Evidence must be relevant before it can be admissible, irrelevant evidence must be excluded. 
Relevance is "assessed in the context of the entire case and the positions of counsel. It requires a determination whether, as a matter of human experience and logic, the existence of a particular fact, directly or indirectly, makes the existence or non-existence of a material fact more probable than it would be otherwise".
Certain evidence does not cease to be relevant or become irrelevant simply because it can support more than one inference. 
Relevance is sometimes divided into 1) logical relevance and 2) legal relevance. Logical relevance, as discussed above, refers to the connection between two facts. Legal relevance is the cost/benefit analysis of the admission of evidence on the basis of probative value outweighing prejudicial effect.
- Hollington v. Hewthorn & Co. Ltd.,  K.B. 587 (C.A.), at p. 594 (“all evidence that is relevant to an issue is admissible, while all that is irrelevant is excluded”)
- R. v. Cloutier 1979 CanLII 25 (SCC), (1979), 48 C.C.C. (2d) 1 (S.C.C.) at 27 and referenced in Watt's Manual of Criminal Evidence, 2010, (Thomson Carswell: Toronto, 2008) at Section 3.0
- R. v. Underwood 2002 ABCA 310 at para. 25
- R v Mohan  2 SCR 9
Evidence must be material to be considered by a court. Material evidence refers to evidence that is contributes to proving a fact that is of consequence to the trial. That is, there must be a relationship between the evidence and a legal issue put to the court.
- R v Gill (1987) 39 CCC (3d) 506 (MBCA)
Rules of AdmissibilityEdit
All courts can only consider admissible evidence.
Where evidence is relevant and material the evidence should be admitted unless their exclusion is justified.
Much of the entirety of the rules of evidence concern the question of what is admissible evidence. As such, admissibly of evidence can be better understood as evidence that is not prohibited by an exclusionary rules. To name the most frequently encountered rules of exclusion include:
- witness competence
- illegally obtained evidence
- conduct on other occasions
In addition to this, there is always a residual common law discretion to exclude evidence.
- See also R. v. Zeolkowski (1987) 333 CCC 231; R. v .Hawkes (1915) 25 CCC 29 (ABCA)
- R v Collins 2001 CanLII 24124 (ON CA) at para. 18, 19
Cyr at para. 116
Even where evidence is relevant, material, and admissible, the court retains a discretionary ability to exclude evidence where the probative value of the evidence is exceeded by its prejudicial effect. 
The law is primarily inclusionary and will tend to admit all evidence that is logically probative of some fact in issue, subject to the rules of exclusion and exception. Where it does not fall into an exclusion or exception issues with the evidence only goes to weight.
The discretionary power allows for a cost-benefit analysis to determine if the value of the evidence to determine the case correctly "is worth the cost of its introduction to the litigation process." This will involve considering the prejudicial effect including the misleading effect and time consumption.
The onus is upon the accused to establish that evidence otherwise admissible should be excluded as prejudicial.
The court should consider the discretion to exclude evidence as follows:
- The judge must determine the probative value of the evidence assessing its tendency to prove a fact in issue in the case including the credibility of the witnesses.
- The judge must determine the prejudicial effect of the evidence because of its tendency to prove matters which are not in issue... or because of the risk that the jury may use the evidence improperly to prove a fact in issue.
- The judge must balance the probative value against the prejudicial effect having regard to the importance of the issues for which the evidence is legitimately offered against the risk that the jury will use it for other improper purposes, taking into account the effectiveness of any limiting instructions.
In a jury setting, the judge must be scrupulous to only permit evidence that is "worthy of jury consideration" and "not whether the jury should accept and act upon the evidence."
In non-jury settings, the judge need not be as scrupulous. The judge is performing a gate-keeping function and so is capable of distinguishing prejudicial evidence. It is unreasonable that the judge is prejudiced from merely hearing evidence.
Where prejudices exist the judges are capable of self-warning of the risks of the evidence. This will often be considered sufficient precaution. A judge who is satisfied he are not prejudice should be taken at his word. R v O’Brien, 2011 SCC 29 (CanLII) at para 18,  2 SCR 485 (“The trial judge was entitled to be taken at his word.”)
The exercise of this discretion requires substantial deference on appeal absent error in principle.
- R. v. Cloutier, 1979 CanLII 25 (SCC),  2 S.C.R. 709, 48 C.C.C. (2d) 1, 12 C.R. (3d) 10
R. v. Smith, 1992 CanLII 79 (SCC),  2 S.C.R. 915, 75 C.C.C. (3d) 257, 15 C.R. (4th) 133
R. v. Moose, 2004 MBCA 176, 24 C.R. (6th) 246, 190 Man. R. (2d) 156
R. v. F. (M.) 2009 ONCA 617 at para. 25
R. v. Mohan,  2 S.C.R. 9, 1994 CanLII 80 (S.C.C.) at pp. 20-21
- R. v. Corbett 1988 CanLII 80 (SCC), (1988), 41 C.C.C. (3d) 385
- R. v. Cyr, 2012 ONCA 919 (CanLII) at para. 96, 97
Mohan, at pp. 20-21
- Cyr at para. 97
- R. v. Jack 1992 CanLII 2764 (MB CA), (1992), 70 C.C.C. (3d) 67, 15 W.C.B. (2d) 92 (Man. C.A.), at p. 86
- R. v. P. (R.) (1990), 58 C.C.C. (3d) 334 (Ont. H.C.) at 347
- Cyr at para. 98 citing R. v. Abbey, 2009 ONCA 624 (CanLII) at para. 89
- see e.g. R v Virani, 2012 ABCA 155 (CanLII) at paras 13-14
TG v Nova Scotia (Community Services), 2012 NSCA 43 at para 75 leave to SCC denied
- see R v Blea, 2012 ABCA 41 at para 49
- R. v. B. (C.R.), 1990 CanLII 142 (SCC),  1 S.C.R. 717, at p. 733
Cyr at para. 103
Probative value concerns the weight put on evidence and not its admissibility.
Determining the probative value of evidence includes considering the "frailties of the evidence, the inferences that may reasonably be drawn from it and the availability of other evidence to prove the same fact."
Probative value includes considering its reliability.
The reliability factor is particularly important when considering expert evidence.
- Morris v. The Queen, 1983 CanLII 28 (SCC),  2 SCR 190 at pp. 99-100 (C.C.C.) pp.192-3 (S.C.R.) - cites example of documents of heroine trade found in accused's residence
- R. v. Leitch and Jno-Baptiste, 2011 ONSC 2597 citing R. v. Pascoe 1997 CanLII 1413 (ON CA), (1997), 113 C.C.C. (3d) 126 (Ont. C.A.)
- Cyr at para. 97
- Cyr at para. 97 citing Mohan at p. 21
Although the first rule of evidence is to admit all relevant evidence there are certain types of relevant evidence that should not be admitted as it will have a prejudicial effect on the fairness of the trial. It is said that there are three grounds of excluding evidence on the basis of it prejudice: "moral", "logical", and "time".
Prejudice is not simply evidence that is harmful to the defence case, but rather it is evidence that will create unfairness by misuse, over consumption of time, or distraction/confusion of issues. The impact will effect "fairness and the integrity of the proceedings"
All judges have a discretion to exclude any evidence on the basis that its prejudicial effect will out-weigh the probative value.
Where evidence is relevant to one count but irrelevant and possibly prejudicial to another count, the court may still admit the evidence but provide a limiting instruction to the jury on the limited use of the evidence.
When the evidence is called by the defence the balance between probative value and prejudicial effect is weighed further in the side of admission. A judge should only exclude evidence where the prejudicial effect "substantially outweighs" the probative value.
When dealing with a jury we must presume that limiting instructions and cautions will be followed and the evidence will be "confined within its proper bounds".
In review, the absence of objection will be a factor in considering if the evidence is significantly prejudicial.
- R. v. Seaboyer, 1991 CanLII 76 (SCC),  2 S.C.R. 577; R. v. Collins 2001 CanLII 24124 (ON CA), (2001), 160 C.C.C. (3d) 85, 150 O.A.C. 220 (Ont. C.A.), at para. 19
- R. v. Mohan 1994 CanLII 80 (S.C.C.), (1994) 29 C.R. (4th) 243 (S.C.C.) 
- R v Cote, (2003) 176 CCC (3d) 89
- R v Shearing,  3 SCR 33
R v Seaboyer,  2 SCR 577
R. v. Clarke, 1998 CanLII 14604 (ON CA)
- Cyr at para. 99
R. v. Corbett, 1988 CanLII 80 (SCC),  1 S.C.R. 670, at pp. 692-693
- R v Jaw, 2009 SCC 42 (CanLII),  3 SCR 26 at para 44, citing R v Jacquard, 1997 CanLII 374 (SCC),  1 SCR 314 at paras 37-38
R v Daley, 2007 SCC 53 (CanLII),  3 SCR 523 at para 58
Moral and Logical PrejudiceEdit
First, there is evidence of moral prejudice which has the potential of creating outrage in the jury and could influence them to make their decision based on emotion. For example, a jury may get the urge to punish an accused for past bad acts even though they are not at issue in the trial. Second, there are logical prejudices that suggest to the jury to make improper inferences, such as relating the accused race with a particular disposition.
In a non-jury setting, concerns of reasoning prejudice and moral prejudice are lessened.
- R v DeKock, 2009 ABCA 225 (CanLII) at paras 33-37, 43-45
R v TB, 2009 ONCA 177 (CanLII) at paras 26-30, 33
R v Blea, 2012 ABCA 41 (CanLII) at para 48
Prejudice arises from evidence that consumes too much time and resources. The trier-of-fact should not have their time wasted with minor evidence that will waste their time and confuse them from the real issues.
The time consumption should be commensurate to its value.
- R. v. Cyr, 2012 ONCA 919 (CanLII) at para. 97
The conduct of the trial, including the admission of evidence, should "not result in the trial being unfair because the accused has been denied a full opportunity to prepare his case, challenge and answer the Crown’s case." 
When considering hearsay tendered by accused the judge may relax the rules of admissibility in order to prevent a miscarriage of justice. This preferred treatment is due to the liberty interests at stake.
- R. v. Albright 1987 CanLII 26 (SCC),  2 S. C. R. 383 at para. 26
- Paciocco and Stuesser, The Law of Evidence, Sixth Edition, at page 118