On October 27, 2023, Paul presented at the Ontario Trial Lawyers Association Fall Conference at the Metro Toronto Convention Centre. The presentation to the medical malpractice section, titled “Bad Doctor or Bad Genes? The Role of Genetics in Medical Malpractice Lawsuits,” explored recent developments in the law allowing physicians and other healthcare professionals to seek genetic testing of plaintiffs as part of the defence to certain medical malpractice claims. The conference paper underlying the presentation was co-authored with Veronica Attia.
The talk focused not on the general doctrinal question of whether a defendant can raise a “genetic cause” theory at trial, but on a specific and developing procedural question: when can a defendant compel a plaintiff to undergo genetic testing as part of the litigation. In Ontario, that question received its first substantive judicial answer in 2021. The framework is still developing.
Why genetics, why now
The procedural debate over genetic testing reflects changes in the underlying science. Genetic testing has become relatively inexpensive, minimally invasive (typically a blood, urine, or saliva sample), and increasingly informative. Whole-exome and whole-genome sequencing now identify genetic etiologies in a meaningful share of cerebral palsy cases that would historically have been attributed to perinatal events. In birth injury claims involving hypoxic ischemic encephalopathy (HIE), meconium aspiration syndrome, or other forms of cerebral palsy, that capability creates both a defence argument (the outcome was genetic) and a discovery question (can the defence force the plaintiff to produce the genetic evidence).
The procedural posture is typically a motion brought by the defence to compel the plaintiff to submit to genetic testing. The plaintiff opposes. The court is asked to balance the defendant’s right to investigate causation against the plaintiff’s privacy and autonomy in their own genetic information.
The Ontario landmark: Klinck v Dorsay
The leading Ontario case is Klinck v Dorsay, 2021 ONSC 6285. The minor plaintiff was born in 2014 and diagnosed at birth with HIE and meconium aspiration syndrome. He was later diagnosed with dyskinetic cerebral palsy. His biological parents, his adoptive parents (the litigation guardians), and the minor plaintiff himself commenced an obstetrical malpractice claim against the midwives and physicians involved in the labour and delivery, alleging that negligent care caused or contributed to the injuries.
The defendants brought a motion seeking an order compelling the minor plaintiff’s biological parents to provide blood samples for genetic testing. The defendants relied on expert evidence opining that the minor plaintiff might have an underlying genetic disorder (most likely a hypomyelinating syndrome) that could be confirmed by genetic testing of the biological parents. The defendants argued that the genetic evidence would be critical to the assessment of both causation and damages.
The plaintiffs opposed on three grounds: the federal Genetic Non-Discrimination Act, SC 2017, c 3 (GNDA), Rule 33 of the Rules of Civil Procedure, and s 105 of the Courts of Justice Act, RSO 1990, c C.43. They argued that the privacy interests in their genetic profiles outweighed the defence interest in compelled testing. They also relied on the thin skull rule from Athey v Leonati, [1996] 3 SCR 458, to argue that any pre-existing genetic vulnerability did not reduce the defendants’ liability and therefore did not justify the testing.
The motion judge ordered the testing, applying a fairness, necessity, and prejudice framework. Three points in the reasoning are worth flagging.
First, on the GNDA. The motion judge held that the Act‘s prohibitions on genetic testing apply to the provision of goods and services and do not apply to (or inform the scope of) medical examinations that may be ordered in a private civil action. The court relied on the Supreme Court’s analysis of the Act‘s scope in Reference re Genetic Non-Discrimination Act, 2020 SCC 17. The GNDA is therefore not a categorical bar to defence-side genetic testing in the litigation context.
Second, on Rule 33. The Rule does not expressly authorize an examining health care professional to obtain samples, conduct analysis, and perform genetic tests. But the Rule contemplates “tests” in broad terms, and the motion judge held that the broad wording supports a discretion to order genetic testing in an appropriate case. The procedural framework already existed; the court read it to extend to the new science.
Third, on the thin skull argument. The motion judge held that the plaintiff must be placed in the position he or she would have been in absent the defendant’s negligence, but not a better position. The defence had provided cogent medical evidence that a genetic cause for the injuries was a reasonable possibility. Where that evidentiary threshold was met, the thin skull rule did not bar the testing.
The result was the first reported Ontario decision ordering genetic testing as part of a defence medical examination in a medical malpractice action.
The persuasive PEI authority: Preece v Nicholson
Preece v Nicholson et al, 2019 PESC 34, addressed similar questions in the Prince Edward Island Supreme Court two years earlier. The plaintiff was delivered by C-section and developed persistent hypoglycemia about one hour after birth. He was later diagnosed with cerebral palsy. The defendants argued that there was a 10 to 25 percent chance that the cerebral palsy was the result of a genetic predisposition rather than the care provided around the delivery.
The defendants sought blood and urine samples for genetic and metabolic testing. The plaintiffs did not consent. The court applied the same fairness, necessity, and prejudice framework that would later be applied in Klinck.
On necessity, the defence demonstrated that one of the plaintiff’s own treating doctors had recognized the need for additional testing, and the defendants’ engaged doctor’s clinical practice included referring children for genetic testing in comparable presentations. On invasiveness, the court accepted that blood and urine samples are minimally invasive, and that the plaintiffs had produced no evidence to support a contrary claim. On the balance of prejudice, the court was satisfied that, given the potentially large quantum of the claim, requiring the defendants to proceed to trial without the genetic evidence would be unfair. The order was granted.
Preece is binding only in Prince Edward Island, but it was applied as persuasive authority in Klinck and reflects the same analytical framework. The two cases together describe the developing law.
The doctrinal anchors
The procedural framework rests on several underlying authorities that are worth identifying for any practitioner working in this area.
Athey v Leonati supplies the substantive backdrop. The thin skull rule does not bar an inquiry into pre-existing vulnerabilities, because the inquiry goes to where the plaintiff would have been absent the breach (the “original position” question), and the crumbling skull adjustment captures any measurable risk that the same outcome would have occurred regardless. Genetic information may be relevant to both halves of that analysis.
Reference re Genetic Non-Discrimination Act, 2020 SCC 17, addresses the constitutional validity and scope of the GNDA. The decision provides the analytical foundation for the Klinck holding that the Act‘s prohibitions are aimed at goods and services and do not constrain medical examinations ordered in private civil litigation.
Sherman Estate v Donovan, 2021 SCC 25, is the privacy-waiver anchor. The Supreme Court confirmed that a plaintiff who commences a civil action waives privacy at least in part. The plaintiff who advances a claim for damages arising from a clinical condition has, by that act, made the condition’s etiology a litigable question. The privacy interest in the underlying genetic data is real but is not absolute.
Section 105 of the Courts of Justice Act and Rule 33 supply the procedural authority. Section 105 requires that the proposed examination be relevant to a material issue in the litigation. Rule 33 governs the conduct of the examination once ordered. Both provisions predate the genetic testing context, and both have proven capable of accommodating it.
Practical observations from the plaintiff side
For plaintiff counsel, three things follow from the Klinck and Preece framework.
The threshold for the defence to meet is “cogent medical evidence” of a reasonable possibility of a genetic cause. That is not a high threshold, but it is also not a free pass. A defence motion that relies on speculation rather than expert opinion grounded in the specific clinical presentation should be challenged. The fishing expedition, as the conclusion of Paul’s presentation put it, remains outside the framework.
The fairness, necessity, and prejudice test is genuinely a balancing exercise, and the plaintiff’s interests are properly part of the balance. Where the testing is invasive, where the quantum of the claim does not warrant the privacy intrusion, where the science being deployed is unsettled, or where the defence has not adequately established necessity, those are arguments to be made on the motion record.
And the substantive defence has to be ready to be tested even when the testing is ordered. A defendant who secures genetic testing under Klinck still has to prove, at trial, what the genetic evidence actually shows. The Athey framework allows the plaintiff to argue thin skull on most of the genetic record and crumbling skull only on what the evidence specifically supports. The procedural battle is the gateway; the substantive battle still has to be fought.
Conclusion
Genetic testing can be useful for the defence, and the courts have made clear that the procedural tools to obtain it already exist in Ontario. The relative ease and low cost of testing, combined with the willingness of courts to apply the fairness, necessity, and prejudice framework, make defence-side motions a developing feature of birth injury and other medical malpractice claims with possible genetic components.
That development cuts both ways. Courts should not allow fishing expeditions, which means defence counsel will need to adduce cogent expert evidence that genetic testing may meaningfully impact causation or damages in the specific case. Where that threshold is met, the testing will likely be ordered. Where it is not, the motion should fail. The framework now in place will be refined in the cases yet to come.
