Evidence - Probative. R v Ansari
In R v Ansari (Ont CA, 2015) Watt JA usefully stated some basic principles of evidence law and their inter-relation [respecting relevance, admissibility, prejudice and whether evidence is probative]:
 The resolution of this ground of appeal requires consideration and application of fundamental principles of the law of evidence. First, the notion of relevance. And, second, the admissibility rule that excludes relevant and material evidence on the ground that its probative value is exceeded by its prejudicial effect.
 Relevance is not an inherent characteristic of any item of evidence. Relevance exists as a relation between, on the one hand, an item of evidence and, on the other, a proposition of fact that the evidence is offered to prove. Relevance is a matter of everyday experience and common sense. An item of evidence is relevant if, by the application of everyday experience and common sense, it renders the fact it seeks to establish by its introduction slightly more or less probable than the fact would be without it: R. v. Luciano, 2011 ONCA 89 (CanLII), 267 C.C.C. (3d) 16, at para. 204.
 Relevance does not exist in the abstract or in the air: Cloutier v. The Queen, 1979 CanLII 25 (SCC),  2 S.C.R. 709, at pp. 730-732; Luciano, at para. 205. Relevance is also relative; we assess and determine it in the context of the entire case in which the evidence is proffered and the positions of counsel in that case: Cloutier, at pp. 730-732; and Luciano, at para. 205.
 To be relevant, an item of evidence need not prove conclusively the proposition of fact for which it is introduced. Nor does the evidence, to be relevant, need to make the proposition of fact more probable than not. An item of evidence is not irrelevant simply because it can sustain more than one inference. The requirement of relevance is met where the item of evidence reasonably shows, “by the application of everyday experience and common sense[,] that the fact is slightly more probable with the evidence than it would be without it”: Luciano, at para. 206.
 Admissibility is a legal concept. Admissibility rules exclude evidence that is both relevant and material on the basis of some policy consideration that the law regards as of sufficient importance to warrant exclusion of evidence that would otherwise assist the trier of fact in ascertaining the truth of the matter at hand. The rule that excludes relevant and material evidence on the basis that its probative value is outweighed by its prejudicial effect is a rule of admissibility.
 The prejudice component of this general exclusionary discretion may involve either or both of two types of prejudice.
 Moral prejudice refers to the risk of an unfocused trial and a conclusion of guilt based on a prohibited chain of reasoning from a general disposition or propensity to guilt of the offence charged. In other words, a finding of guilt that is based on character, not conduct: R. v. Handy, 2002 SCC 56 (CanLII),  2 S.C.R. 908, at paras. 31 and 139.
 Reasoning prejudice involves the distraction of the trier of fact from their proper focus on the offence charged by the introduction of evidence of other incidents that consume undue time and may be accorded more weight than should be their due: Handy, at para. 31 and 144.
 When invited to exclude relevant, material and otherwise admissible evidence on the basis that its prejudicial effect predominates over its probative value, a trial judge will consider the individual constituents of the rule – probative value and prejudicial effect – and then balance them to determine which predominates.
 The assessment of probative value involves consideration of the strength of the evidence; the extent to which it supports the inferences the proponent seeks to have drawn from it; and the extent to which the matters the evidence tends to prove are at issue in the proceedings: R. v. B. (L.); R. v. G. (M.A.) (1997), 1997 CanLII 3187 (ON CA), 116 C.C.C. (3d) 481 (Ont. C.A.), at para. 23.
 An assessment of prejudicial effect should take into account:
i. the degree of discreditable conduct disclosed by the evidence; A trial judge’s decision about where the balance settles between probative value on the one hand and prejudicial effect on the other is accorded a high degree of deference by appellate courts. Where a trial judge has applied the proper principles, weighed the probative value of the evidence and its potential prejudice and decided the issue of admissibility, appellate courts will not lightly intervene: R. v. Arp, 1998 CanLII 769 (SCC),  3 S.C.R. 339, at para. 42; R. v. Bevan, 1993 CanLII 101 (SCC),  2 S.C.R. 599, at p. 613; R. v. B. (C.R.), 1990 CanLII 142 (SCC),  1 S.C.R. 717, at pp. 733-734; R. v. Samuels, 2013 ONCA 551 (CanLII), 310 O.A.C. 175, at para. 47; B. (L.); G. (M.A.), at para. 51.
ii. the extent to which the proposed evidence may support an inference of guilt on the sole basis of bad character;
iii. the extent to which the evidence may confuse issues; and
iv. the ability of the accused to respond to the evidence.
B. (L.); G. (M.A.), at para. 24.
 A final point concerns prophylactic measures undertaken by the trial judge to reduce the risk of reasoning or moral prejudice. A limiting instruction that explains the proper use of this evidence and enjoins prohibited reasoning is of critical importance in ensuring a fair trial: R. v. Vukelich (1996), 1996 CanLII 1005 (BC CA), 108 C.C.C. (3d) 193 (B.C. C.A.), at para. 51.