Under what circumstances will a defendant be found guilty of perverting the course of justice by failing to explain or deny evidence against him?

^3. The instruction provided: "'In this case defendant has testified to certain matters. If you find that the defendant failed to explain or deny any evidence against him introduced by the prosecution which he can reasonabl[y] be expected to deny or explain because of facts within his knowledge, you may take that failure into consideration as tending to indicate the truth of this evidence and as indicating that among the inferences that may reasonabl[y] be drawn therefrom those unfavorabl[e] to the defendant are the more probable. [] 'The failure of a defendant to deny or explain evidence against him does not, by itself, warrant an inference of guilt, nor does it relieve the prosecution of its burden of proving every essential element of the crime and the guilt of the defendant beyond a reasonable doubt. [] 'If a defendant does not have the knowledge that he would need to deny or to explain evidence against him, it would be unreasonable to draw an inference unfavorable to him because of his failure to deny or explain this evidence.'" (People v. Lamer, supra, 110 Cal.App.4th at pp. 1468-1469.)