What is the test for determining custody of a child?

It is trite law that a court must determine the custody of a child based on the best interests of that child. The meaning of this test was addressed by L’Heureux-Dubé J. (dissenting in the result) in Young v. Young, 1993 CanLII 34 (SCC), [1993] 4 S.C.R. 3 at ¶71, 72, 80, and 82: ¶ 71 A determination of the best interests of the child encompasses a myriad of considerations, as child custody and access decisions have been described as “ones of human relations in their most intense and complex form”. In contrast to most issues that come before the courts, such decisions are “person-oriented” rather than “act-oriented” and require an evaluation of “the whole person viewed as a social being”… ¶ 72 In making a determination as to the best interests of the child, courts must attempt to balance such considerations as the age, physical and emotional constitution and psychology of both the child and his or her parents and the particular milieu in which the child will live. … Probably one of the most significant factors in many cases will be the relationship that the child entertains with his or her parents. This must necessarily encompass such considerations as the strength of the emotional ties and the role of the person who has provided primary care in the life of the child. … ¶ 80 In assessing all the relevant considerations, courts must be careful that the ideals of parental sharing and equality do not overcome the lived reality of custody and access arrangements and that the child’s needs and concerns are accommodated and not obscured by abstract claims of parental rights. This is not to say that the parent’s interests may not coincide with the child’s interests or that a court may never validly take a parent’s interests into consideration. However, to further the best interests of the child, a recognition of the close relationship between the needs of the child and the needs of the remaining family unit of which he or she is a part is essential. … … ¶ 82 In the final analysis, when considering the best interests of the child, it may be a virtue rather than a sin for the judge to be pragmatic and take into consideration both the strengths and shortcomings of the parties and the limits of human nature. To do so is only to recognize that, in some circumstances, the perfect may be the enemy of the good. Courts must always be mindful that not only the benefit but also the real cost and burden of all custody and access arrangements ultimately falls on the children themselves.

Thereafter, in Gordon v. Gertz, 1996 CanLII 191 (SCC), [1996] 2 S.C.R. 27, the court held there is no presumptive starting point for what is in the best interests of a child. Instead, the court must undertake an inquiry that provides individual justice for every child before the court on a custody dispute. McLachlin J. (now C.J.), writing for the majority, framed the test at ¶46: “The child’s best interest must be found within the practical context of the reality of the parents’ lives and circumstances …”