What is the risk of a court appointing its own expert?

Veit J's reasoning in Bilinski v. Wagerin supra provides a useful lens through which to assess the risk of the court appointing its own expert. There is a danger that such expert's evidence is likely to carry great weight, to the potential detriment of the assessment of contrary evidence led by the parties. As pointed out by Counsel for Appellant, in this case the parties do not have psychiatric evidence to date and the problem in getting reasonable rebuttal evidence so close to trial is the issue the court‑appointed expert is meant to address. However, this then creates difficulties for the parties to question or rebut the evidence of the court‑appointed expert.