Rules of Court throughout Canada demand that a party who wants to rely on an expert must give the other side, about one month before the hearing, a copy of the expert's report with "a full statement of the proposed evidence in chief of the witness". (See Tax Court of Canada General Procedure r. 145(2)(b).) There are two reasons for these rules:
"the general purpose ... 'that it is essential for the trier of fact to know the basis of an expert opinion so that the opinion can be evaluated. ... The second purpose is to allow the opposing party to know the basis of the expert's opinion so that they or their counsel can properly prepare for, and conduct, cross-examination of the expert, and if appropriate, secure a responsive expert opinion.'" (Para. 21.)
"Ms. Vallière [the expert] admitted on cross-examination that the opinion presented in her Report was based upon data she collected, quantitative analysis conducted on the data collected and then drawing consequent ratios." (Para. 23.) But Crown "Counsel also made a choice not to offer these working files to Appellant Counsel or to this Court at any point, even after they became an issue." (Para. 31.) So, Justice Campbell refused to allow the expert to testify or for the Government to rely on her report. And Justice Campbell didn't think it proper to order an adjournment in the hearing so the Government could correct its tactical decision because doing so would be "promoting additional time, delays and expenses" which is the opposite of what the Court rules strive for. (Paras. 32 to 33.)
Decisions like these often stress "fairness" to the parties and "a just, speedy and inexpensive determination of the proceedings on its merits". (Para. 20.) But hidden behind these explanations is the goal of Courts: to make reasoned decisions that seem fair, so that the public will respect the law and the administration of justice in the land. Lawyers are "officers of the Court", the purpose of whom is to help the judge make a wise decision. If one side can "ambush" or surprise the opposing lawyer with an expert's opinion, that lawyer hasn't time to prepare, to ask good questions, offer a responding expert, or give the judge other information to help the judge make a wise and respectable decision. So, through these tactics, the honor of the Court suffers and not just the private interests of the parties.
See Bekesinski v. The Queen, (2014 TCC D. Campbell)