The High Court handed down a record number of unanimous decisions in 2009 - the first full year of Robert French's tenure as Chief Justice of Australia - a UNSW analysis shows.

The study of the High Court's decisions in 2009 by Dr Andrew Lynch and Professor George Williams, from the University of New South Wales' Gilbert + Tobin Centre of Public Law, shows that for almost 45 percent of all cases decided the Court was able to reach a single opinion as to the outcome.

The report was presented at the ninth annual Constitutional Law Conference the Art Gallery of New South Wales.

"This is a remarkable result," Dr Lynch said. "If we look at the average rate of unanimity under the previous four Chief Justices, the highest figure is about one case in every four. Yet in 2009, the Court decided almost half its cases with total agreement among its members."

The authors said the consensus was not simply due to the retirement of Justice Michael Kirby in February last year. Kirby was nicknamed 'The Great Dissenter' on account of his regular disagreement with the views of his colleagues on the Court.

"The rate of dissent on the Court last year certainly fell," said Lynch, "but that alone cannot account for the prevalence of unanimous opinions. A number of factors may be in play, quite aside from the nature of the cases that went before the Court."

Lynch and Williams argue that any change in the composition of the bench was likely to affect the inner workings of the Court, but this was particularly relevant when the change involved a new Chief Justice taking the reins.

"Our understanding of the ability of Chief Justices to shape consensus is limited," said Lynch, "but depending on the individual, the office of Chief Justice provides a number of ways to effect change. In trying to understand the increase in unanimity and corresponding drop in dissenting opinions in 2009, the fact that this is now the 'French Court' is likely to be significant."

Data from the study showed, however, that the Court was still just as likely to split over constitutional issues as it was in the past.

"2009 was an historically significant year in the development of constitutional doctrine, with cases such as the challenge to the Rudd government's fiscal stimulus payments producing surprising results," Lynch and Williams said. "The significance and difficulty of the constitutional issues the Court faced explains why the general trend to consensus did not carry over in many of these cases."

The study also found that certain judicial partnerships appeared to be in a state of flux.

Although Justices William Gummow and Kenneth Hayne have invariably co-authored opinions in constitutional cases in recent years, in 2009 Hayne wrote twice as often with new Justice Susan Kiefel than he did with Gummow.

2009 was also notable as the first year in which three of the Court's serving Justices were women. Only four women have ever been appointed to the High Court bench.

Read Andrew Lynch's opinion piece on the topic in The Australian newspaper.

Contact: Dr Andrew Lynch | 9385 9654 | a.lynch@unsw.edu.au