Short answer. Yes, it can be raised — but a diagnosis is not the test. What counts is his state at the moment of execution, and the law does not require an unimpaired mind, only that he knew the nature of his estate, the proper objects of his bounty, and the character of the testamentary act.
What the law says
In order to make a will it is essential that the testator be of sound mind at the time of its execution.
Civil Code, Article 798 — Soundness of Mind Required. Read the full provision →
What the law says
To be of sound mind, it is not necessary that the testator be in full possession of all his reasoning faculties, or that his mind be wholly unbroken, unimpaired, or unshattered by disease, injury or other cause.
Civil Code, Article 799 — What 'Sound Mind' Means. Read the full provision →
What the law says
If the testator was insane, or otherwise mentally incapable of making a will, at the time of its execution
Civil Code, Article 839 — Grounds to Disallow a Will. Read the full provision →
One moment decides it
Article 798 requires the testator to be of sound mind at the time of its execution. Everything in a capacity dispute is therefore pinned to a single date. A decline described in hindsight, records from a year after the signing, or a diagnosis that came later address a different question, and Article 801 confirms the direction of travel: supervening incapacity does not invalidate a will that was effective when made. The practical consequence is that the strongest material is contemporaneous — what was written down about him in the weeks around the signing, and by whom.
Sound mind is deliberately a low bar
Article 799 corrects the assumption most families arrive with. To be of sound mind, it is not necessary that the testator be in full possession of all his reasoning faculties, or that his mind be wholly unbroken, unimpaired, or unshattered by disease, injury or other cause. It is enough that at the time of making the will he could know the nature of the estate to be disposed of, the proper objects of his bounty, and the character of the testamentary act. Forgetfulness, confusion about the day, needing help with daily life, even a formal diagnosis, do not by themselves fail that test.
Who has to prove what
Article 800 starts from a presumption of sanity and then places the work squarely on the challenger: The burden of proof that the testator was not of sound mind at the time of making his dispositions is on the person who opposes the probate of the will. There is one shift, and it is narrower than people expect. Where the testator was publicly known to be insane within one month or less before making the will, the burden moves to whoever upholds it, who must show it was made during a lucid interval. Both elements are demanding — a short window, and a condition known publicly.
Where it is raised, and with what
Article 839 lists the grounds for disallowing a will, and this one appears as: If the testator was insane, or otherwise mentally incapable of making a will, at the time of its execution. Read the rest of that list before settling on capacity, because the same facts often support the stronger ground of undue and improper pressure and influence, particularly where the person who benefited most arranged the signing and chose the witnesses. What decides these cases is medical notes dated close to execution, the account of the attesting witnesses and the notary who watched him sign, and the terms of the will itself.
Cases citing this provision
These Supreme Court decisions cite the provision above. We list them so you can read them yourself; the summaries of what each decided are not ours to give.
- Marita S. Cabas vs. Bernadita Vargas Feranil Vda. De Penaverde, G.R. No. 272590, April 23, 2025 — read the decision on LawPhil →
Related provisions
- Civil Code, Article 798 — Soundness of Mind Required
- Civil Code, Article 799 — What 'Sound Mind' Means
- Civil Code, Article 800 — Presumption of Sanity
- Civil Code, Article 801 — Supervening Incapacity
- Civil Code, Article 839 — Grounds to Disallow a Will