Detailed Answer

Short answer: To challenge a will in Oregon on grounds of lack of testamentary capacity or undue influence you need evidence showing the testator either did not understand the nature and consequences of making the will, or that another person improperly coerced or controlled the testator so the will reflects that person’s intent rather than the testator’s. Typical evidence includes medical records, witness statements about the testator’s mental state and interactions, contemporaneous notes or recordings, changes in beneficiary patterns, financial records, and proof of a confidential relationship or active procurement.

How Oregon law frames the issues

Oregon law governing wills is found in Chapter 112 of the Oregon Revised Statutes (ORS). The statutes set rules about execution and validity of wills, and Oregon courts apply well-established common-law standards when disputes arise. See ORS Chapter 112 for the statutes on wills: https://www.oregonlegislature.gov/bills_laws/ors/ors112.html.

Issues about capacity and undue influence often overlap with guardianship and incapacity matters addressed in ORS Chapter 127. For general reference see: https://www.oregonlegislature.gov/bills_laws/ors/ors127.html.

Testamentary capacity: legal standard and evidence

Legal standard (plain terms): At the time the will was signed, the testator must have understood (1) the nature and effect of making a will, (2) the nature and approximate extent of his or her property, and (3) the natural objects of his or her bounty (the people who would normally be expected to inherit) and how the will disposed of property among them. In practice courts ask whether the testator possessed enough mental ability to make an informed decision about the will.

Helpful types of evidence to show lack of capacity:

• Medical and mental-health records showing dementia, delirium, acute illness, stroke, psychiatric disorder, medication effects, or cognitive testing results near the time the will was signed.
• Physician or treating-care provider declarations describing the testator’s cognitive condition at signing.
• Testimony from witnesses who talked with the testator around signing (friends, neighbors, care staff) about confusion, memory loss, or inability to understand the consequences of the document.
• Video or audio recordings showing the testator’s mental state or inability to comprehend the will.
• Handwriting or capacity expert reports (neuropsychologists, geriatric psychiatrists) analyzing whether the person had the required capacity.
• Evidence of medication changes, hospitalizations, or intoxication at or just before signing.
• Comparative wills and the testator’s prior statements about their intent — big unexplained departures can support an inference of incapacity when paired with other proof.

Undue influence: legal standard and evidence

Legal standard (plain terms): Undue influence occurs when another person uses pressure, manipulation, or a position of dominance to overpower the free will of the testator and induce a disposition that would not reflect the testator’s true wishes. Courts look for proof that the influencer had opportunity and motive, that the testator was susceptible, and that the influencer actively procured or participated in preparing the will.

Common evidence used to prove undue influence:

• Proof of a confidential or dependent relationship between the testator and the alleged influencer (e.g., caregiver with access to the testator’s finances and daily life).
• Signs of active procurement — the influencer arranged for the attorney, controlled communications, was present when the will was prepared, or urged rapid execution.
• Unnatural or suspicious dispositions — a close non-relative inherits a large share over children or a prior well-established plan is abruptly changed in a way that benefits the influencer.
• Opportunities and motive — access to the testator, sudden transfer of assets, or financial motive to obtain the estate.
• Witness testimony describing pressure, threats, isolation, or coercive tactics used by the influencer.
• Documentary evidence — contemporaneous letters, emails, notes, bank records showing transfers, or unsigned drafts showing the influencer’s involvement.
• Admissions or statements by the influencer (or third parties) that indicate they controlled or directed the will-making.

How courts weigh evidence

Courts assess the totality of circumstances. No single piece of evidence is usually dispositive. A combination of suspicious circumstances, proof of control or procurement, and the testator’s vulnerability is often needed. Many courts recognize a rebuttable presumption of undue influence when a person in a confidential relationship who actively procures a will benefits from it; that presumption shifts the burden and requires the proponent to show the will was the free and independent act of the testator.

Burden of proof: Contest procedures and standards (preponderance vs. clear and convincing) can vary by claim and local rules. In practice, undue influence claims often require strong proof; consult a lawyer early to understand the evidentiary standard a local court will apply in your case.

Practical steps to gather and preserve evidence

1. Immediately preserve physical evidence: original will copy (if available), drafts, envelopes, witness names, and any related documents.
2. Request medical records and medication logs from hospitals, clinics, and care facilities for the relevant period. Ask for records by written request and keep copies.
3. Interview and obtain written statements from witnesses who saw the testator around the time of signing, including neighbors, caregivers, roommates, attorneys, and notaries.
4. Collect communications: emails, text messages, voicemail, letters, and social media that show who was urging changes or controlling the testator’s communications.
5. Secure financial records that show sudden transfers, payments to the influencer, unusual withdrawals, or changes to account beneficiaries.
6. Obtain an expert evaluation: neuropsychological testing or a medical expert’s declaration can carry weight when capacity is disputed.
7. Document the timeline: create a clear chronological summary of events, health changes, contacts with the influencer, and when the will was executed.
8. Preserve devices and backups: if there may be recordings, emails, or files on phones/computers, preserve those devices and consult counsel about forensic collection.

Timing, procedures, and next steps

Time is important. File concerns with the probate court promptly after probate begins; delay can limit options and reduce available evidence. Oregon has procedural rules for contests to wills and probate proceedings that affect deadlines and forms. Because procedural rules matter, contact a lawyer who handles wills and probate disputes quickly to preserve rights and evidence.

Hypothetical example

Imagine an elderly person with mild dementia signs three months before signing a new will that disinherits adult children and leaves everything to a non-relative caregiver. Evidence helpful to a challenge might include the physician’s notes showing cognitive decline, records showing the caregiver controlled access to the testator, bank records showing large transfers to the caregiver, testimony from friends that the testator did not recognize family members, and the fact that the caregiver arranged the attorney visit and stayed in the room. Together, those facts could support a finding of lack of capacity or undue influence.

Helpful Hints

• Preserve evidence immediately: medical records and witness contact information are time-sensitive.
• Keep a dated timeline of events and suspicious transactions — courts rely on chronology.
• Get experienced probate counsel early. Even if you are unsure, an attorney can advise on whether the facts support a contest and next procedural steps.
• Ask medical providers for records in writing and request copies of any cognitive testing or psychiatric notes close to the signing date.
• Collect witness statements quickly while memories are fresh; signed, written declarations are useful.
• Avoid confronting suspected influencers in ways that could destroy evidence or provoke retaliation; instead, consult an attorney on safe steps to preserve proof.
• If you suspect financial exploitation, notify the bank and consider a forensic accounting of unusual transactions.

Disclaimer: This article provides general information about Oregon law and common types of evidence used in will contests. It is not legal advice and does not create an attorney-client relationship. For advice about a specific situation, consult a licensed Oregon attorney who handles probate and will-contest matters.