Common practice, breach of duty and jury trials: the history of Mercer v Commissioner of road Transport and Tramways (1936)

Mercer v Commissioner for Road Transport and Tramways (NSW) is the High Court of Australia authority usually cited for the proposition that a defendant does not necessarily refute an allegation of negligence by showing that it followed a common practice. While this article does not challenge that characterisation of the case, an analysis of the historical context in which the decision was made suggests that Mercer is as much about the appropriate boundaries of appellate review of civil jury verdicts as an attempt to set out substantive principles. Mercer reminds us that much can be learnt about legal rules by considering both the contemporary legal debates to which a decision responds as well as the procedural form in which decisions about substantive rules were taken.