Most states require a will to be in writing, signed by the testator (or by someone else at the testator's direction and in their presence), and signed by at least two witnesses who are present at the same time and who typically must also be disinterested, meaning they do not stand to benefit under the will. Some states additionally require or permit self-proving affidavits, notarization, or specific witness-competency rules, and a minority allow oral (nuncupative) wills in very limited circumstances, such as imminent death on a battlefield or during a final illness.

Strict compliance with execution formalities was historically an all-or-nothing requirement — a single missing witness signature could invalidate an otherwise clearly intended will — but a growing number of states have adopted a harmless-error or substantial-compliance doctrine, allowing a court to excuse a formality defect if there is clear and convincing evidence the document reflects the testator's genuine testamentary intent. Whether a jurisdiction follows strict compliance or a harmless-error approach can be outcome-determinative when a defect is found.

Juricratic represents the execution-formalities question as a gating dial — since a document that fails execution requirements in a strict-compliance state may not be a valid will at all — and separately models the harmless-error rescue probability in jurisdictions that recognize it, rather than collapsing the two into one figure.

Estate planning and probate attorneys review the exact execution circumstances — who signed, in what order, whether witnesses were present together, whether a self-proving affidavit was used — because a defect discovered after the testator's death is often unfixable, and whether the governing state applies strict compliance or a harmless-error doctrine can determine whether that defect is fatal.