Short answer: in Ontario, parenting disputes are decided under the federal Divorce Act for divorcing spouses and the Children’s Law Reform Act otherwise, and both statutes ask a single question: what is in the best interests of the child. The factors under that test are largely observable things, who actually cares for the child, how stable each household is, how exchanges go, whether anything in either home bears on the child’s safety. Observable things can be documented, and documented conduct is what lets a judge decide on evidence instead of refereeing two competing stories. That is the entire, narrow role of a custody investigation. This article is about when one helps, what it produces, and the versions that reliably blow up.
The only question the court asks
Nothing in a parenting case is scored for grievance. The Divorce Act’s section 16 factors run through the child’s needs, the strength and stability of each relationship, each parent’s willingness to support the child’s relationship with the other parent, and any family violence and its impacts, and Ontario’s CLRA mirrors the same test. We keep a standing plain-language reference on how courts treat surveillance evidence against that test in Legal Authority, and the one-sentence version is this: courts credit patterns documented from lawful vantage points, and they discredit conflict dressed up as diligence. Every decision below follows from that sentence.
When an investigation is proportionate, and when it is not
The cases where documentation genuinely serves the child share a feature: a specific, articulable concern that observable evidence can confirm or dispel. Suspected impairment during parenting time, including driving with the child. A parent who claims to exercise parenting time personally while the child is actually left elsewhere. An undisclosed resident of the other household whose presence matters to safety, a disqualifying partner, a prohibited contact. Care patterns that contradict what is being sworn in affidavits: the child repeatedly late or absent from school during the other parent’s weeks, medical needs going unmet. In each of these, a short, defined period of lawful observation answers a question the court will actually ask.
The test that fails: wanting to know what your ex is doing. New relationships, ordinary social lives, how they spend money on themselves, none of it is a best-interests factor absent a concrete link to the child’s wellbeing, and surveillance aimed at it reads in evidence exactly as what it is. When a caller cannot name the specific concern and the decision it would inform, the honest professional answer is that there is nothing to investigate yet, and we say so at intake.
What a custody investigation actually documents
Fieldwork, where justified, is unspectacular by design. Exchanges documented from public vantage points: times, attendance, demeanour observable from a distance, no interaction with anyone. Parenting-time spot checks that answer the narrow question asked, was the parent present, was the child taken to school, who drove, conducted on a handful of defined dates rather than as an open tap. Where impairment is the concern, observable public conduct: the route from the bar to the driver’s seat with the child in the car. Everything timestamped, logged with vantage points, and reported in the format we build for court across every practice area, because a report that cannot survive cross-examination is worse than no report.
Around the fieldwork sits quieter work that often matters more: verifying who actually lives at an address through lawful records and observation, confirming employment claims that bear on proposed schedules, and assembling the documentary timeline, orders, communications, school records your lawyer obtains, into something a judge can follow in ten minutes.
The self-help that backfires
The failure modes are consistent enough to list. A tracking device on the other parent’s vehicle: unlawful on a car you do not own, and it converts your safety concern into their harassment evidence, as we set out in our GPS tracking guide. Covert recordings of the child, or sending the child back with questions to answer: courts treat both as conscripting the child into the conflict. Round-the-clock DIY surveillance of the other household, drive-bys, sitting outside the home: under the Divorce Act’s family-violence lens, a pattern of following and watching can itself be framed as harassment, and you should assume it will be. Going through the other parent’s phone, email or accounts: unlawful access, and everything it touches becomes tainted. The pattern behind all of these is the same: evidence gathered in anger serves the anger, not the child, and judges have seen every version of it.
Working with counsel
The strongest custody files run investigator work through the family lawyer: a defined question, a defined window, a report that goes to counsel and fits the motion it was commissioned for. That sequencing also keeps costs proportionate to what the motion needs, billed the way we bill everything, hourly and itemized with a written scope first. Counsel briefing an investigator for the first time can start with our note on instructing investigators; parents can start with a consultation that will tell you honestly whether there is anything here worth documenting at all, through our child custody and family practice.
Not legal advice
This article is general information, not legal advice. Parenting litigation is governed by fact-specific statutory tests, and surveillance decisions in family matters carry real legal and relational risk. Decide with a family lawyer, not in reaction to a bad weekend.
Frequently asked questions
Is it legal to have my ex followed during a custody case?
Lawful surveillance of an adult from public vantage points, conducted by a licensed investigator, is legal in Ontario, but legality is only half the test in a parenting case. The observation must serve a specific best-interests question, impairment during parenting time, absent care, an undisclosed household member, and stay proportionate to it. Open-ended watching of an ex-partner’s life reads to a court as conflict, not evidence, and can be framed as harassment.
Will a court accept surveillance evidence in a custody dispute?
Courts regularly accept documentation gathered lawfully from public vantage points, particularly pattern evidence bearing directly on best-interests factors: exchanges, presence and absence during parenting time, observable safety concerns. Weight depends on lawfulness, proportionality and quality of documentation, timestamps, vantage points, contemporaneous logs. Evidence obtained through trespass, interception, device access or tracking is a different story, and can damage the party who obtained it.
Can I put a GPS tracker on my ex’s car to prove they’re unsafe with the kids?
No. Installing a tracker on a vehicle you do not own has no statutory permission in Canada, can engage criminal harassment and mischief exposure, and in a family case it hands the other side ready-made evidence of controlling conduct. If impairment or unsafe driving with the child is the genuine concern, lawful observation on defined dates answers it without destroying your position.
How much does a custody investigation cost?
It is billed like all of our work: hourly, per investigator, with mileage itemized and a written scope agreed before anything starts. Because proportionality is the entire game in family files, custody assignments are deliberately narrow, defined questions over a handful of defined dates, which keeps them at the modest end of surveillance work rather than the open-ended end.
Sources
- Canada, Divorce Act, s. 16 (best-interests factors, including family violence and each spouse’s support of the child’s relationship with the other). Accessed August 7, 2026.
- Ontario, Children’s Law Reform Act, s. 24 (best-interests test for parenting orders). Accessed August 7, 2026.