The narrow legal grounds for setting a will aside - and why "it is not fair" is not one of them.
A will contest is a court challenge to the validity of a will, brought by someone with standing - usually a person who would inherit if the will were invalid, such as an heir under the intestacy statute or a beneficiary under an earlier will. Being treated unequally, or left out, is not itself a ground. People are generally free to leave their property as they wish, and the law asks only whether the document was validly made, not whether it was kind or sensible.
The recognised grounds are few. Improper execution: the formalities the state requires were not met. Lack of testamentary capacity: at the moment of signing, the maker did not understand the nature of the act, the general extent of their property, or the people who would naturally be expected to benefit. The test is lower than people assume, and a diagnosis of dementia is evidence rather than an answer, because capacity is assessed at the time of signing. Undue influence: someone in a position of dominance overbore the maker's free will, typically shown circumstantially through a confidential relationship, the influencer's involvement in procuring the will, isolation of the maker, secrecy, and a sudden departure from a long-standing plan. Fraud or forgery, and revocation, complete the list.
Two features shape these cases in practice. Many wills contain a no-contest (in terrorem) clause providing that a beneficiary who challenges forfeits their gift; states differ sharply on enforcement, and a common approach is to enforce it except where the challenge was brought with probable cause - so the clause raises the stakes without making a well-founded claim impossible. And the challenge must be brought within a period fixed by state statute that is typically short, often running from the will's admission to probate or from the notice sent to interested persons: this is the deadline people miss, because it can expire while a family is still grieving and is materially shorter than ordinary civil limitation periods. That period is set by the statute of the state in question and is not stated here.
Even a successful contest may not produce what the challenger wants. Invalidating a will normally revives the previous valid will if one exists, and only if none exists does the estate pass under the intestacy statute - which may leave the challenger no better off. It is also worth separating a contest from the related claims often mistaken for one: a claim that the executor is mishandling the estate, a claim on a lifetime gift or a beneficiary designation obtained by undue influence, or a surviving spouse's statutory elective share, each of which has its own route and does not require the will to be invalid.
Get advice early, because the filing period is usually short and the evidence that decides these cases degrades quickly. What matters most is contemporaneous: the drafting lawyer's file and notes, medical records from around the signing date, the witnesses to the execution, bank and account records showing lifetime transfers, and the pattern of who had access and who arranged the appointment. Ask whether the real complaint is actually about the will at all - a large lifetime transfer, a changed beneficiary designation, or an executor's conduct after death are separate claims with separate remedies and sometimes better prospects. If there is a no-contest clause, ask specifically how your state treats it and whether the claim has the probable cause that usually preserves the gift. Contests are expensive, are usually funded by the challenger rather than the estate, and are frequently mediated; ask for a realistic assessment of both the merits and the likely cost before filing, and ask what a successful outcome would actually leave you with.
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