s sixthly, there are some cases in which such a direction will be ineffective and they may occur where one or at least perhaps more than one of the following considerations apply: where out-of-court statements of co-accused contain grave allegations of bad character of the accused; where there is evidence irrelevant to any issue between the Crown and the accused and which could not have been led at a separate trial of the accused but is admissible as to an issue between the Crown and the co-accused and is highly prejudicial to the accused; where evidence irrelevant to any issue between the Crown and the accused is admissible against a co-accused, and as against the co-accused serves to corroborate or reinforce the evidence of an eyewitness against the co-accused, and as a result the jury would be likely to believe the eyewitness, not only in what he or she may say against the co-accused, but also in what he or she may say as against the accused, at least where the Crown places heavy reliance upon that witness to implicate the accused and the evidence is open to serious challenge.