Byrd and Byrd (Conditional Admission of Expert’s Evidence)

In the matter of *Byrd and Byrd*, Le Poer Trench J considered the admissibility of expert evidence in circumstances where the factual basis for the expert's opinion had not been fully established. The dispute concerned the admission of a report prepared by an expert, Ms D, attached to her affidavit.

The central legal issue before the court was whether section 79 of the *Evidence Act* requires that the admissibility of expert opinion evidence be dependent on the proper disclosure and proof of its factual basis. This involved considering whether a "basis rule," as understood at common law, applied under the *Evidence Act*, or if the Act intended for such issues to be managed through the court's general discretion.

Le Poer Trench J, referencing *Daniel v Western Australia* and *Quick v Stoland*, concluded that section 79 of the *Evidence Act* does not mandate a strict basis rule. The court reasoned that the legislative intent, as reflected in the Australian Law Reform Commission's Report No 26, was to allow expert opinion evidence to be admitted even if its factual basis is not fully proven by admitted evidence. The weight to be given to such evidence, and its ultimate admissibility, is to be determined by the tribunal of fact, with the court retaining a general discretion to exclude evidence if its prejudicial effect substantially outweighs its probative value or if excessive time would be expended in its reception.

Consequently, the court ordered that the report of Ms D attached to her affidavit filed on 27 December 2011 be conditionally admitted to evidence. The final determination of the report's admissibility and the weight to be accorded to it was reserved for the conclusion of the taking of evidence in the case as a whole.