Can a party challenging a will's validity subpoena the deceased's medical records in Ontario?

Yes, generally. Where testamentary capacity is genuinely in issue, a party to an Ontario will challenge can seek production of the deceased's relevant medical records, since they're often central evidence for showing what the testator's cognitive state actually was around the time the will was made. This typically requires a formal request or court order directed at the relevant healthcare providers or institutions, rather than the records simply being handed over informally, and the deceased's own privacy interests, while reduced after death, don't disappear entirely from the analysis.

Courts generally focus on relevance and proportionality: records from the period closest to when the will was signed, and records specifically addressing cognitive function, memory, or the kinds of conditions relevant to capacity, are more likely to be ordered produced than a person's entire lifetime medical history. Records unrelated to capacity, or from long before or after the relevant period, may be resisted as overly broad or not relevant to the actual issue in the case. Because obtaining medical records often takes real time and can face resistance, anyone planning to rely on this kind of evidence in a capacity dispute should raise it with a lawyer early rather than waiting until closer to trial.