Proof of causation in informed consent cases : establishing what the plaintiff would have done

A degree of judicial caution in accepting the assertion of a plaintiff as to what he or she would have done, if fully informed of risks, is clearly evident upon a review of decisions applying the common law. Civil liability legislation in some jurisdictions now precludes assertion evidence by a plaintiff. Although this legislative change was seen as creating a significant challenge for plaintiffs seeking to discharge the onus of proof of establishing causation in such cases, recent decisions suggest a more limited practical effect. While a plaintiff’s ex post facto assertions as to what he or she would have done if fully informed of risks may now be inadmissible, objective and subjective evidence as to the surrounding facts and circumstances, in particular the plaintiff’s prior attitudes and conduct, and the assertion evidence of others remains admissible. Given the court’s reliance on both objective and subjective evidence, statistical evidence may be of increasing importance.