Expert undermines probative value of their own evidence by going beyond the scope of their expertise

share on

 

Eastbound Estate Pty Ltd v DC Consolidated Investments Pty Ltd [2024] VSC 40

In this case, the court gave little weight to expert evidence that was considered partisan and substantially reliant on solicitors’ instructions, not on the expert’s field of specialised knowledge.

Background

Pursuant to a clause granting a conditional power to terminate, the defendant purported to terminate its contract for the sale of land with the plaintiff. The plaintiff rejected the validity of the termination. The dispute between the parties centered on the construction of the clause, and whether the preconditions to the power conferred by it were satisfied to enable its valid exercise by the defendant.

Expert evidence

The plaintiff relied on the expert reports of senior traffic engineer Mr VG and town planner Ms AP. The defendant relied on the expert report of town planner Mr DC, who responded to the opinions set out in the expert report of Ms AP. The defendant also relied on expert report of senior traffic engineer Mr JLW, which was provided in response to the opinions set out in the expert report of Mr VG.

Joint reports by Ms AP and Mr DC, and by Messers VG and JLW were also tendered, setting out their points of agreement and disagreement.

Mr DC’s impartiality was lengthily questioned during cross-examination, and the plaintiff submitted that where DC’s evidence disagreed with that of Ms AP, it should be rejected as partisan. To support this, the plaintiff tendered email correspondence between Mr DC and his instructing solicitors regarding the preparation of his expert report. It was suggested that Mr DC was identifying arguments in order for the defendant to advance its case.

The court accepted this submission to some extent, and found that the email correspondence and DC’s evidence itself show that his opinions were partially informed by considerations which were not within his area of expertise, some of which relied substantially on the defendant’s solicitors’ instructions. The court said that the probative value of Mr DC’s evidence was diminished because of his “ultracrepidarian efforts” (being efforts outside Mr DC’s sphere of knowledge) as well as his incorporation of broader considerations of the impact of the conditions to the defendant’s business into his opinions. [95]

The court was critical of Mr DC’s response to the evidence as to certain conditions, which was held as having the tendency to incorporate other considerations external to his expertise, based substantially on background assumptions provided directly from the defendant’s solicitors, into his evidence. The court said that whilst an element of Mr DC’s evidence can be explained by reference to the defendant’s case as to the proper construction of “too onerous to perform”, which appears likely to have been an assumption implicit within his brief, his evidence as to these matters is not informed by his relevant expertise. [99] Some of Mr DC’s evidence was informed by considerations external to DC’s expertise, and because of this limited weight was attached to these conclusions. [104]

Similarly, some aspects of Mr JLW’s opinion were found to have been informed by considerations outside the scope of his expertise. The court said that the framing of the defendant’s case and its contended construction meant that it was inevitable that its witnesses would be required to opine on areas outside his field of specialised knowledge and rely on assumptions provided in his instructing briefs, to some extent. This detracted from the probative value of his evidence. [96]

Specifically, the court also found that similar to Mr DC’s evidence, considerations of the performance of the relevant conditions of the contract which were clearly beyond the scope of Mr JLW’s expertise should not have been relevant to his conclusions. Thus, the court rejected Mr JLW’s evidence, to the extent that it was informed by his view of those considerations beyond the scope of his expertise. [100]

The court ultimately ruled that defendant’s purported termination of the Sale Agreement was invalid.

Key takeaways

  • Experts must only opine on matters which fall squarely within their field of specialised knowledge.
  • Where an expert report contains opinions going beyond the scope of the expert’s field of specialised knowledge, the probative value of the evidence may be undermined.
  • If the case theory and the assumptions provided to the expert would result in the expert giving an opinion outside their field of expertise, lawyers should consider whether other experts are needed in the matter.

 

Read the full case here.

Your search for a winning expert stops here.

AUSTRALIA