“While more readily identified in criminal proceeding, the rule in Browne v. Dunn is equally applicable to family law trials. Some examples of its application can be found in Liu v. Huang, 2020 ONCA 450 at para. 13-25 and Alajalian v. Alajajian, 2019 ONSC 4678 at para. 17.
The rule can be summarized as follows. If a party intends to impeach a witness called by the opposite party, the party who seeks to impeach must give the witness an opportunity, while the witness is in the witness box, to provide any explanation the witness may have for the contradictory evidence: Browne v. Dunn, 1893 CanLII 65, at pp. 70-71; R. v. Quansah, 2014 ONCA 237 at para. 75.
The rule in Browne v. Dunn is a rule that ensures trial fairness. It ensures fairness to the witness whose credibility is attacked, fairness to the party whose witness is impeached, and fairness to the trier of fact. With respect to the last principle, it ensures that the trier of fact will not be deprived of information that might show the credibility impeachment to be unfounded and thus compromise the accuracy of the verdict: Quansah, para. 77.
As stated in Evidence in Family Law, by Harold Niman, at para. 7:15
If you intend to challenge the credibility of a witness you must put the disputed facts or documents to them in cross examination or run the risk of the ancient but still applied rule in Browne v. Dunne.
This is based upon the principle of fairness, so that every relevant witness shall have an opportunity to address important facts or documents. You are not permitted to “blindside” the other side of a case by remaining silent about an important and relevant fact or document which you intend to introduce in your part of the trial and thus rely upon as part of your own case. This is obvious if the “hidden” fact or document relates to credibility, but just as applicable to any other relevant portion of the case.
In this case, a number of violations have been admitted. In these cases, I have the discretion to decide the remedy to be afforded for the breach. The remedy should depend on a number of factors and the circumstances of the case. These factors include the seriousness of the breach, the context of the breach, the timing of the objection, the position of the offending party, any request to recall a witness, and the availability of that witness for recall: Quansah, at para. 117.
In a family law proceeding, two remedies are available. First, I could consider the breach of the rule when assessing a witness’ credibility and deciding the weight to attach to that witnesses’ evidence. Alternatively, I could allow counsel to recall the witness whose evidence was impeached without notice and allow them to give evidence on these narrow issues: Curley v. Taafe, 2019 ONCA 368 at para. 31.”