11 August 2017: QLD Floods Class Action (the first case) - What happens when the expert changes his opinion?


The Court noted that “the plaintiff’s case on liability and causation turns almost exclusively on the evidence of two experts” dealing with:

(a) the unsatisfactory operation of the Dams, including a failure to engage in “reasonably prudent flood operations”; and
(b) simulations of the water flows that would have occurred with proper flood management.

The engineering / hydraulic expert’s first report was prepared two and a half years ago, since which time he prepared three more reports – the most recent of which was the subject matter of the plaintiff’s application. That report, as well as being last minute, included a revision of the expert’s earlier opinion. The change had come about to account for matters put forward by the defendant, and criticisms of earlier reports.

The plaintiff, understandably, wanted to file revised expert evidence reflecting the expert’s final view (and make consequent changes to the statement of claim). This was opposed, including on the basis that prejudice would flow to the defendants from vacating the trial date including the potential unavailability of their counsel who had a long involvement with the matter. On the other hand the plaintiff argued that their expert had acted properly by candidly approaching whether his opinion remained correct and should be revised, and his making adjustment for the opposing party’s experts points, as is required by the Court’s compulsory Expert Code of Conduct. The plaintiff submitted that it would be inappropriate to force it to commence the trial with a report which the expert no longer adhered to.

The Court drew heavily on five criterion set out by the High Court of Australia in Aon Risk Services Australia Ltd v Australian National University (2009) 239 CLR 175, stating as follows:

However, just because an expert retained by a party changes his opinion or advances a further opinion does not give that party an unfettered right to rely on that change much less amend its pleading to reflect it. Other factors must be considered including[1]:
(i)    the point the litigation has reached relative to the trial (Aon at [102]);
the extent of the delay and the costs associated with the delay including the wider effects of delay upon the Court and other litigants (Aon at [102] and [93] to [95]);
whether the party applying has had sufficient opportunity to plead their case (Aon at [102]);
such prejudice as may be assumed and demonstrated (Aon at [102]); and
whether the party applying for the amendment has provided an explanation …(Aon at [103])”

In this matter the consequences of allowing the new report included delaying trial to at least December 2017, possibly later. The Court noted that it was undesirable for proceedings to be set back at such a late stage, prejudicing the defendant. It considered that the plaintiff’s new approach to expert evidence genuinely arose out of outcomes of issues which arose in the past 12 months, but that the plaintiff should have acted sooner to address the substantive expert issues (“the delay was occasioned through neglect, and that is a matter that weighs against the granting of leave”).

The Court refused to accept the defendant’s submission that the delay was the result of a deliberate forensic decision by the plaintiff, which the plaintiff was trying to backtrack on.

In the end, the Court allowed the newly formulated expert evidence and associated pleading amendment, stating:

Even allowing for the delay, it would be unjust to force the plaintiff to pursue a case which is strongly based on opinions in an expert's report which that expert feels obliged to correct and when much of the unfairness occasioned to the defendants from doing so can be addressed by delaying the hearing and the making of an appropriate order as to costs.

The Court also refused to allow a pleading which

purports to confer on the plaintiff the right to rely on any form of alternative simulation after judgment has been delivered and regardless of whether or not, on the state of the existing evidence, it may have failed to prove causation or whether the defendants have had a fair opportunity to meet that alternative simulation

The take home message is that lawyers should:

  1. carefully monitor evolving expert evidence and the status of any other evidence which relies on changing evidence; and
  2. raise as early as practicable any revision of evidence.

This is of course especially poignant the closer a proceeding approaches to trial.

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