In his recent decision in Aecon Construction Group Inc. v. The Queen, Justice Angers of the Tax Court of Canada adopted a practical and sensible approach to the problem of an expert witness potentially being conflicted out of a tax appeal because of having been approached by one of the parties which then decides not to commission a report from that expert.
In Aecon, the disputed turned on the fair market value of mining properties in 1993. The taxpayer contended that the value was $32 million while the Crown contended that the value was $3 million. The taxpayer relied on two expert reports. The Crown originally relied upon one expert report. Prior to trial Crown counsel approached two other experts, Mr. F and Mr. R, both of whom had already been approached by the taxpayer. The Crown wrote counsel for the taxpayer taking the position that the taxpayer’s limited contact with Mr. F should not disqualify him from acting for the Crown in the tax appeal. The taxpayer’s counsel took the position that both Mr. F and Mr. R were disqualified and the Crown took this motion in the Tax Court to have the status of Mr. F determined in advance of trial.
Justice Angers quoted the famous statement of Lord Denning in Harmony Shipping Co SA v. Davis et al. as reproduced by Justice O’Keefe of the Federal Court in Abbott Laboratories v. Canada (Minister of Health), 2006 F.C. 340.
 Accordingly, the principles require that the Court balance the interests of the party seeking to retain an expert witness and the party seeking to protect its confidential information. In that regard, counsel for Pharmascience raises the danger of expert witnesses being contacted simply to deprive an opposing party of their expertise. This danger was eloquently described by Lord Denning in Harmony Shipping Co SA v. Davis et al,  3 All ER 177 (C.A.):
If an expert could have his hands tied by being instructed by one side, it would be very easy for a rich client to consult each of the acknowledged experts in the field. Each expert might give an opinion adverse to the rich man, yet the rich man could say to each, “Your mouth is closed and you cannot give evidence in court against me” ….. Does that mean that the other side is debarred from getting the help of any expert evidence because all the experts have been taken up by the other side? The answer is clearly No …. There is no property in an expert witness as to the fact he has observed and his own independent opinion of them. There being no such property in a witness, it is the duty of a witness to come to court and give his evidence in so far as he is directed by the judge to do so.
Justice Angers concluded that the limited contact between the taxpayer and Mr. F was not sufficient to support a disqualification:
 Neither party in this motion, has been able to clarify the nature of the confidential information that may or may not have been communicated. Mr. F’s affidavit does not disclose if he has, in fact, received any and the appellant did not cross-examine Mr. F on his affidavit. It is therefore unclear as to the risk associated with disclosing said information or if, it will cause a prejudice to the appellant. No evidence was put forward that allowing the respondent to retain Mr. F. would prejudice the appellant.
 In the light of the evidence presented, one cannot conclude that Mr. F and the appellant shared sufficient information for either one to expect that whatever that information may be would be kept in confidence or is privileged. Mr. F was never retained, no retainer agreement or confidentiality agreement was signed and there is no evidence that the appellant would have requested Mr. F not to discuss the matter with others. Mr. F did not open a file, did not invoice the appellant nor received any payment, nor was he asked to perform any services. It appears to me that the discussions Mr F had with the appellant in 2001 were of an informal nature and nothing more than an attempt to see if Mr. F shared their point of view. In his affidavit, Mr. F did not recall discussing specific legal strategy other than the fact that he refused to be “creative” in responding to CRA’s position. He cannot recall the documents he reviewed nor did he retain any documents. He also said that early on, he communicated to the appellant that, on the basis of previous experience with Watts, it was unlikely that the appellant would agree with his firm’s method of valuation. That is hardly the foundation necessary for the appellant to shield Mr. F from being retained by the opposing party and provide his opinion. [Emphasis added]
What is clear from this decision is that a limited contact with a potential expert witness will not normally be sufficient to disqualify that witness. There must be real concerns about confidential information shared with that potential expert and the taxpayer must be able to prove those concerns to the satisfaction of a judge if the potential disqualification is raised before the court.