What Is Meant By Adverse Inference?
An Adverse Inference or Negative Inference May Arise When a Court Deems That a Party Has Failed to Produce Supporting Evidence or Testimony and Such a Failure Indicates That the Evidence, If Produced, Would Disfavour the Party.
Understanding the Principle of Adverse Inference As An Evidentiary Rule Arising From Failure to Produce Evidence
An adverse inference may arise where a party fails to testify, or where a party fails to lead evidence that is in control of the evidence, and from such a failure the court may thereby presume that the reason for the absence of the evidence or the absence of testimony is that such would negatively affect the party who fails to provide the testimony or the evidence.
An adverse inference presumption arises from the expectation that where a litigant is in possession of evidence or control of a witness, the litigant would provide the evidence or present the witness unless the evidence or witness is harmful to the case of the litigant. The legal doctrine was provided within the cases of, among others, Tiwari v. Chevalier, 2022 ONSC 3071, and Lane v. Kock, 2015 ONSC 1972, which respectively stated:
 The effect of the failure of a party to testify or to call a material witness or other evidence, is summarized as follows in Sydney N. Lederman, Alan W. Bryant & Michelle K. Fuerst, The Law of Evidence in Canada, 4th ed. (Markham: LexisNexis Canada, 2014) at p. 386:
In civil cases, an unfavourable inference can be drawn when, in the absence of an explanation, a party litigant does not testify, or fails to provide affidavit evidence on an application, or fails to call a witness who would have knowledge of the facts and would be assumed to be willing to assist that party. In the same vein, an adverse inference may be drawn against a party who does not call a material witness over whom he or she has exclusive control and does not explain it away. Such failure amounts to an implied admission that the evidence of the absent witness would be contrary to the party's case, or at least would not support it.
The choice to apply an adverse inference is discretion as was explained within the Court of Appeal case of Parris v. Laidley, 2012 ONCA 755, wherein it was said:
 Drawing adverse inferences from failure to produce evidence is discretionary. The inference should not be drawn unless it is warranted in all the circumstances. What is required is a case-specific inquiry into the circumstances including, but not only, whether there was a legitimate explanation for failing to call the witness, whether the witness was within the exclusive control of the party against whom the adverse inference is sought to be drawn, or equally available to both parties, and whether the witness has key evidence to provide or is the best person to provide the evidence in issue.
The principle of adverse inference is the legal version of saying, if you got it, then flaunt it; and, if a party fails to do so, the court may presume that a party who fails to use evidence does so because the evidence would be unfavourable.