The test as to where this will be permissible is similar to that used for general psychiatric evidence; the individual seeking to adduce expert testimony must have been suffering from a genuine personality disorder outside the understanding of the tribunal, and this must have some effect of rendering their confession unreliable.[20] Where such evidence is adduced, it has been made clear by R v O'Brien[21] that the jury must be instructed they are not under obligation to accept such evidence, but must consider it with regard to the confession in issue. A second situation where evidence has been permitted is where there are allegations that a confession may have been coerced, or given as a form of compliance rather than voluntarily. In R v Blackburn[22] the Court of Appeal ruled that the area of coerced confessions fell outside the experience of ordinary individuals, and thus expert evidence may be adduced where this is at issue.