The function of evaluator in a child custody dispute is different from that of a therapist in a traditional, clinical setting. The practitioner must keep these roles separate. Trying to be both the therapist and forensic evaluator for the same children or family is inappropriate and complicates both the therapy and the evaluation.

A custody evaluator is a forensic specialist whose skills include an engaging interview style, an understanding of family relationships and interpersonal dynamics, an appreciation for child and adult developmental issues, and familiarity with family law in the local jurisdiction.

Treating clinicians are advocates or agents for children and ideally are partners with parents or guardians in the therapeutic alliance. In contrast, the forensic evaluator, while guided by the child's best interests, has no duty to the child or his or her parents. The forensic evaluator reports to the court or attorney involved rather than to the parties being evaluated. Thus, the aim of the forensic evaluation is not to relieve suffering or to treat, but to provide objective information and informed opinions to help the court render a custody decision. Forensic evaluators must be mindful of this role and convey this in full to all parties before beginning the evaluation.

Ethical considerations are highlighted in forensic evaluations. Evaluators should consider whether they are qualified to perform the evaluation, have the time and flexibility to work within the judicial system, have set fees that are fair, are able to remain unbiased and unaligned with one side of the case, and have sufficiently ruled out any conflict of interest. The evaluator normally guards against providing advice, which the courts will consider expert, in areas in which he or she has insufficient training, education, or experience.