The Short Answer

In Florida, challenging a will for undue influence or lack of capacity usually requires evidence about the testator’s condition and the circumstances surrounding the signing—especially who was involved, what changed, and whether the testator acted independently. Florida law also recognizes situations where a presumption of undue influence can shift the burden of proof, which can significantly change the outcome of a will contest.

What Florida Law Says

Florida allows a will (or part of a will) to be declared invalid if it was procured through improper conduct like undue influence, and Florida places specific burdens on the parties in a will contest. Practically, that means your evidence often needs to address (1) the testator’s mental state and vulnerability, and (2) whether a beneficiary improperly participated in getting the will made or changed.

The Statute

The primary law governing undue influence in a will is Fla. Stat. § 732.5165.

This statute establishes that a will is void if its execution is procured by fraud, duress, mistake, or undue influence (and even a portion can be void while the rest remains valid).

For who has to prove what in a will contest (including presumptions), Florida also relies heavily on Fla. Stat. § 733.107, which addresses the burden of proof and recognizes a presumption of undue influence that can shift the burden under the Evidence Code.

For lack of capacity, Florida’s Probate Code requires that the person making the will be of sound mind. See Fla. Stat. § 732.501.

Why You Should Speak with an Attorney

Even when families “know something wasn’t right,” courts decide these cases based on admissible evidence and legal standards—not suspicion. A probate attorney can help identify what evidence actually matters, preserve it, and present it in a way that fits Florida’s burden-shifting rules.

• Strict Deadlines: Will contests are time-sensitive, and waiting can limit your options—especially once probate litigation begins and assets start moving.
• Burden of Proof (and Presumptions): Under Fla. Stat. § 733.107, the proponent must first show the will was properly executed, and then the contestant must prove the grounds (like undue influence or lack of capacity). If a presumption of undue influence applies, the burden can shift—often becoming the central battleground.
• Evidence Hurdles: The most persuasive evidence is often not what people expect (for example, medical records and witness testimony about the signing can matter more than family opinions about “unfairness”).

Common evidence used to prove undue influence may include: testimony from witnesses present around the signing; communications showing isolation, pressure, or control; proof a beneficiary arranged the lawyer, meeting, witnesses, or kept the will; sudden changes from a long-standing estate plan; and evidence of dependency (caregiving, finances, transportation, medication control).

Common evidence used to prove lack of capacity may include: medical records near the signing date (diagnoses affecting cognition, medication effects); testimony from the drafting attorney and witnesses about the testator’s understanding; records showing confusion about assets/heirs; and evidence of delusions, dementia progression, or inability to understand the nature and effect of making a will.

If you’re dealing with a situation where the original will is missing or there are disputes about who should control the estate while a contest is pending, you may also want to read: probating a copy of a lost will in Florida and disputes over who should be appointed executor (personal representative).

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Disclaimer: This article provides general information under Florida law and does not create an attorney-client relationship. Laws change frequently. For legal advice specific to your situation, please consult with a licensed attorney.