How courts evaluate a person’s capacity and claims of undue influence in South Dakota wills

Short answer: To challenge a will in South Dakota on the grounds of lack of testamentary capacity or undue influence you will generally need contemporaneous medical and mental-health records, testimony from witnesses who saw the testator’s condition or the person’s relationship with the alleged influencer, documentary evidence of suspicious circumstances (sudden changes, unusual gifts, or isolated drafting), and any attorney or drafting records that show who controlled the process. The person contesting the will bears the burden of proving the challenge, typically by showing the evidence is more likely than not.

Detailed Answer

This section explains what the court looks for and the kinds of evidence that are persuasive under South Dakota probate practice and the Uniform Probate Code principles that South Dakota follows (Title 29A of the South Dakota Codified Laws). See South Dakota statutes on probate and wills: Title 29A — Uniform Probate Code (SDCL) and the wills chapter: Chapter on Wills.

1) Testamentary capacity — what the court must find

To have capacity to make a valid will the testator must, at the time the will was executed, understand:

• the nature and effect of making a will (that the document disposes of property at death),
• the nature and approximate extent of the testator’s property, and
• the natural objects of the testator’s bounty (who the testator’s family or close relations are) and the plan of distribution those persons would expect.

If the testator lacked this understanding because of dementia, delirium, severe mental illness, or medication effects, the will can be attacked for lack of capacity.

Evidence that supports lack of capacity

• Medical records showing diagnoses (dementia, stroke, delirium, psychosis) and notes about cognitive testing or confusion around the time the will was signed.
• Testimony from treating physicians, nurses, or physician assistants describing the testator’s mental state near signing.
• Depositions or affidavits from friends, family, caregivers, or neighbors who observed memory loss, confusion, or unusual behavior.
• Medication records showing sedatives, high-dose narcotics, or new medication changes that impair comprehension.
• Attorney or notary notes: if the drafting attorney recorded misunderstandings or refused to proceed, that helps; if there are no notes and the attorney relied entirely on the influencer, that is suspicious.
• Video or audio showing the testator’s mental state while signing (if available and admissible).

2) Undue influence — what courts look for

Undue influence exists when a person uses overpowering persuasion or pressure so that the resulting testament reflects the influencer’s will rather than the testator’s free intent. South Dakota courts consider both the relationship and the circumstances surrounding the execution.

Common categories of persuasive evidence of undue influence

• Relationship and opportunity: Evidence that the beneficiary had a close, confidential relationship with the testator and frequent, unsupervised access (private caregivers, roommate, trusted advisor).
• Active procurement: The beneficiary arranged or directed the will-drafting — choosing the attorney, arranging the meeting, supplying or writing the will, or being the only person present at execution.
• Suspicious circumstances: Extreme or unnatural dispositions (close family disinherited for no clear reason), large last-minute changes, or the testator’s signature when they previously expressed different wishes.
• Isolation: Documentation that the testator was intentionally cut off from family or regular advisors before signing.
• Undue benefit matched with control: Transfers of property during life to the beneficiary shortly before death or sudden changes to financial accounts coordinated with the new will.

Typical evidence used to show undue influence

• Emails, texts, letters, voice messages or notes showing the influencer pressured the testator or tried to control communications.
• Eyewitness testimony that the influencer coached answers or prevented other people from attending signing.
• Bank and transfer records showing unusual gifts or withdrawals consistent with the alleged influence.
• Attorney intake notes, draft wills, and notations showing who requested changes or almost exclusively provided instructions.
• Affidavits from family members about prior testamentary intent that contradicts the challenged will.
• Evidence the influencer benefited disproportionately and immediately after the testator executed the instrument (e.g., immediate title transfers, beneficiary updates).

3) Burden and standard of proof

If you challenge a will, you must present evidence to the probate court establishing lack of capacity or undue influence. In practice, courts require persuasive proof — typically a preponderance of the evidence (more likely than not) — that the testator either lacked the necessary mental capacity at execution or that the will resulted from undue influence. The judge weighs medical evidence, witness testimony, and the pattern of events surrounding execution.

4) Practical steps to build or defend a challenge

1. Preserve the original will and any contemporaneous drafts. Do not alter them.
2. Secure medical and prescription records around the time the will was signed. Ask treating providers for notes, cognitive testing, and hospital records.
3. Collect communications (texts, emails, social media messages) and bank records showing transfers or unusual activity.
4. Identify and interview witnesses: the signing attorney, notary, caregivers, friends, and family who interacted with the testator near execution.
5. Get sworn affidavits describing observed condition or suspicious conduct; consider deposition testimony in probate litigation.
6. Consult (and if needed, retain) a medical or psychiatric expert experienced with testamentary capacity to review records and, if appropriate, provide an expert opinion admissible in court.
7. Document any pattern of isolation or control by a potential influencer, including who arranged appointments and transportation and who paid medical bills.

Helpful Hints

• Act quickly. Medical records and witness memories fade. Probate time limits can bar claims if you wait too long.
• Get the original will and any codicils; the court prefers originals as primary evidence.
• Look for contemporaneous notes in the drafting attorney’s file — attorneys sometimes make helpful observations about the testator’s capacity and who gave instructions.
• Preserve electronic evidence (screenshots, metadata). If you can’t save it yourself, tell an attorney what to subpoena quickly.
• If you are the attorney who witnessed a will, keep clear notes about the testator’s competence and who attended the meeting; such notes can be decisive later.
• Don’t confront alleged influencers aggressively — it can prompt document destruction or contamination of witnesses. Instead, preserve evidence and contact an attorney.
• Remember that sudden changes in a will aren’t automatically invalid. Courts balance the totality of circumstances: capacity evidence, who instructed the change, and whether the change fits the testator’s prior statements.

Next steps: If you believe a will should be challenged for lack of capacity or undue influence, gather the records and witness names listed above and consult a probate attorney licensed in South Dakota who handles will contests. An attorney can evaluate whether the evidence likely meets the required legal standard and can guide you through filing a petition in the county probate court.

Disclaimer: This article is for general information only and is not legal advice. It does not create an attorney-client relationship. For advice about a specific situation, consult a licensed South Dakota attorney.