Malpractice litigation is now a substantial cost in the provision of healthcare. Despite new attitudes of Australian courts towards medical evidence, expert reports remain the cornerstone of most medical negligence cases. There is evidence that hindsight bias, which may cause the expert to simplify, trivialise and criticise retrospectively the decisions of the treating doctor, is inevitable when the expert knows there has been an adverse outcome. If possible, outcome information should be withheld from experts providing reports. If outcome information is not withheld, courts should be made aware of the probability of hindsight bias.