proving a will

Proving a will is the legal procedure by which someone persuades a probate court to accept a testamentary document as a valid will. Depending on the jurisdiction, proving a will is usually satisfied by showing that the will was in writing, the will was signed by the deceased person, and that the signing of the will was witnessed in accordance with statutory formalities. These requirements serve to provide reliable evidence of the decedent’s intent, guard against any fraud, and streamline the probate process by providing uniformity and standardization for what constitutes a will.

Some states have adopted the harmless error rule, which allows a court to admit a will to probate despite defects in its execution, if there is clear and convincing evidence that the decedent intended the document to operate as a will. For example, California follows this approach by permitting probate of a formally defective will when such intent is proven. To reduce barriers to creating a valid will, many states also permit holographic wills, which are handwritten by the decedent and typically do not require witnesses. These wills generally must contain material provisions in the testator’s handwriting and, in some jurisdictions, must be dated to help establish authenticity, capacity, and priority over other testamentary documents.

In proving a will, courts traditionally admit extrinsic evidence to resolve any latent ambiguity, which arises when the language of the will is clear on its face but is unclear upon further investigation. For example, there would be latent ambiguity when a will gives property to the testator’s friend “John Smith”, however the testator had two friends with the exact same name. In contrast, courts traditionally do not allow extrinsic evidence to prove the testator’s intent when there is patent ambiguity, meaning the will has uncertain words or phrases that appear on the face of the will. For example, there would be patent ambiguity if a testator merely writes they will give a house to “him”, without explaining who they are referring to by “him”. Today, courts increasingly allow extrinsic evidence for patent ambiguity.

[Last reviewed in January of 2026 by the Wex Definitions Team] 

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