“Where the parties wish to engage a joint expert but do not agree on a matter relating to the engagement, either of them may apply to the court for directions: Family Law Rules, r. 20.2(9). In my view, that provision includes disagreements that arise after the expert has been engaged and before his or her report is complete.
To ensure the efficacy and reliability of the jointly retained expert evidence, the parties are required to “cooperate fully with the expert and make full and timely disclosure of all relevant information and documents to the expert”: r. 20.2(12). The court may draw any reasonable inference against any party that fails to do so: r. 20.2(12).
The predominant purpose of retaining a joint expert is to avoid the battle of competing experts. That usually means a savings of time and expense, and often aids in resolution of some or all issues.
A neutral, independent, jointly retained expert investigates the issue(s), sets forth the facts on which his or her opinion is based, sets out the documents he or she relied on, and provides an opinion and the rationale for that opinion: r. 20.2(2),(3), and (5). The expert owes a duty to the court to be fair, objective and non-partisan. That duty to the court trumps any obligation owed by the expert to a party: r. 20.1(3).
Where the parties have engaged a joint expert, no other litigation expert may present opinion evidence on that issue unless the court orders otherwise: r. 20.2(13). Thus, once the expert report is finalized and absent a supplementary report, the parties are not permitted to adduce other expert evidence on the issue without leave of the court.”