Courts do not allow a will to be challenged simply because an heir or beneficiary is unhappy with its terms; a person must fit within a recognized legal ground and generally must have standing as an 'interested party' — typically someone who would inherit more under a prior will or under intestate succession if the challenged will were set aside. The commonly recognized grounds include lack of testamentary capacity, undue influence, fraud in the execution or inducement of the will, duress, and failure to comply with the state's required execution formalities.

Each ground has its own elements and its own allocation of the burden of proof, and they are not mutually exclusive — a single contest often pleads several grounds in the alternative, such as lack of capacity together with undue influence, since the facts supporting one frequently overlap with facts supporting another (a vulnerable, isolated testator is more susceptible to both incapacity findings and influence). Most states also impose a relatively short limitations period for filing a will contest, running from probate or from notice to interested parties.

Because a will contest's success typically depends on how strongly the facts support each pleaded ground rather than on a single bright-line rule, Juricratic models each ground's likelihood of success as its own dial and lets a user see how the combined probability of setting aside the will shifts as evidence on any one ground changes.

Estate litigators evaluating whether to file a will contest first confirm the challenger has standing and that the limitations period has not run, then assess which recognized grounds the available evidence actually supports, since courts hold contestants to a real evidentiary burden and an unsupported challenge risks a fee-shifting or no-contest-clause consequence depending on the jurisdiction and the will's own terms.