“Assessments, while not binding on the judge deciding a matter, can be useful, even persuasive, in assisting the court to determine whether a proposed custodial arrangement would be beneficial to a child. They combine professional training with investigative powers to produce first-hand, independent information and insights not otherwise available. For various reasons, however, not the least of which is their cost and the time necessary to prepare, they are not routinely ordered. A judge must be satisfied the cost/benefit considerations clearly favour the ordering of an assessment. The importance of a cautious approach to ordering assessments was explained by Blishen J. in Glance v. Glance (2000) CarswellOnt 3169 at para 12:
Assessments by their very nature are intrusive. They are also expensive and time consuming. There must be evidence sufficient to satisfy the court that the reasons for requiring the assessment more than offset any harm that might be incurred by ordering the assessment. The paramount concern must be the best interests of the child. The order for an assessment must have a proper evidentiary basis and it must be in the best interests of the child to order such an assessment.
In addition, they should not be used to find evidence to make a case or to enlist the assessor to provide support for the parent’s factual narrative (see Jonkman v. Murphy, 2011 ONSC 3917).”
Donaldson (McGuire) v. Hill, 2020 ONSC 4330 (CanLII) at 16-17