Expert opinions are often a key battleground in Canadian class actions, both at the certification stage and at the common issues hearing stage. The B.C. Court of Appeal’s decision refusing to grant leave to appeal in Abbotsford (City) v. Mostertman sets out several important principles concerning pre-certification production of an expert’s files in a proposed B.C. class action:

• A party may apply for production. There is no general right to document discovery before certification. However, a party may apply for production of documents, including an expert’s files, in the context of a certification application. The applicant bears the onus of justifying the requested production.
• A production request must be precise. To avoid bogging down the certification process, a party seeking pre-certification production must be sufficiently precise in their request and show that the requested documents will inform the certification process.
• A court has discretion to order production. In determining whether a court should exercise its discretion to order production of an expert’s files, the court should consider the content of the experts’ reports and any other evidence relevant to the production request. The court should also consider the objective of proportionality and be alive to the possibility that one production order may lead to another, and so on.
• A refusal to produce may impact weight. If disclosure is refused, it remains open to the opposing party to argue on the certification application that the court should give little or no weight to the expert’s opinions due to the perceived gaps in information.

Abbotsford is an important decision for putative class action defendants. It teaches that there is no default rule—for either plaintiffs or defendants—favouring production of an expert’s files. In each case, the court must determine whether, in all the circumstances, the party seeking production has justified the request—which must be precise.