R. v. U.K., 2023 ONCA 587, September 11, 2023, at paragraphs 70 to 72, and 77 and 78:

A statement or evidence by an accused person found to have been deliberately fabricated (or concocted) is a type of post-offence conduct. Our courts have developed special rules applicable to alleged fabricated statements or evidence because of the risk posed by this type of inference of inadvertently shifting the burden of proof by turning a disbelieved statement or evidence into positive evidence of guilt.

The law draws a distinction between statements or testimony by an accused which are disbelieved, and therefore, rejected, and statements or testimony which are found to be fabricated in an effort to avoid culpability. A disbelieved statement or evidence has no evidentiary value. A statement or evidence found to be fabricated in an effort to avoid liability may be considered as circumstantial evidence of guilt: 

There must be independent evidence of fabrication before a trial judge may instruct a jury that they may consider deliberate fabrication by an accused for the purpose of avoiding liability as circumstantial evidence of guilt. The requirement of independent evidence of fabrication exists in order to maintain the distinction between statements or evidence which are merely disbelieved and statements or evidence which are found to be fabricated. Independent evidence in this context means evidence beyond disproving the exculpatory statement. There must be evidence that the exculpatory statement was deliberately made for the purpose of avoiding liability: Coutts, at p. 203, O’Connor, at paras. 18-21; Al-Enzi, at para. 39; R. v. Laliberté, 2016 SCC 17, [2016] 1 S.C.R. 270, at para. 4.

Where the allegation of fabrication relates to an out-of-court statement, independent evidence of fabrication may be found in the circumstances in which the statement was made, including the timing, as well as its logical implausibility, level of detail, or internal inconsistencies in the statement. 

However, where fabrication of trial evidence is alleged, what may be considered as evidence of fabrication is more restricted. Unlike for out-of-court statements, where there is an allegation of fabrication of trial evidence, the circumstances surrounding the testimony, such as logical implausibility or internal inconsistencies, cannot constitute independent evidence of fabrication. This principle was put as follows by O’Connor J.A. in O’Connor: “Before an adverse inference may be drawn, there must be evidence capable of showing fabrication apart from both the evidence contradicting the accused’s testimony and the fact that the accused is found to have testified falsely at trial”…