Detailed Answer

When someone asks a court to invalidate or modify a will in Washington because the person who signed the will lacked the mental capacity to make it or was subject to undue influence, the court looks at the totality of the evidence. Two different problems are at issue:

1) Lack of testamentary capacity (mental capacity)

To make a valid will a person must, at the time of signing, generally:

• Understand the nature and extent of their property;
• Know the natural objects of their bounty (close family and those who might reasonably expect to inherit); and
• Understand the legal effect of signing a will and the disposition they were making.

Evidence that helps prove lack of capacity includes:

• Medical records and treating-provider notes documenting dementia, delirium, stroke, psychosis, severe depression, medication side effects, or other conditions that impair understanding;
• Testimony from doctors, neuropsychologists, psychiatrists, or other clinicians about the person’s mental status near the time the will was signed;
• Witness testimony describing the person’s appearance, speech, memory, coherence, or ability to explain their assets and relationships when signing the will;
• Contemporaneous statements, letters, emails, journals, or recordings showing confusion or impaired decision-making;
• Evidence of severe physical illness, hospitalization, or hospitalization notes around the signing date;
• Handwriting analysis or other forensic evidence if there is a question whether the signature is genuine or was made by someone else.

2) Undue influence

Undue influence occurs when someone exerts pressure or control so intense that the will produced reflects the influencer’s wishes rather than the testator’s free and independent choice. Washington courts evaluate the relationship and circumstances, not only isolated acts. Relevant evidence includes:

• Proof of a confidential or dominant relationship between the testator and the beneficiary (for example caregiver, close adviser, or someone controlling access to the testator);
• Active procurement by a beneficiary or influencer — e.g., they arranged the will signing, selected the attorney, or took the testator to the lawyer without independent advice;
• Unnatural or sudden changes in the will that favor a particular person who previously received little or nothing;
• Lack of independent advice — no separate lawyer or independent witnesses present, or the lawyer who drafted the will also benefited from it;
• Evidence the testator was isolated from family and friends or had restricted contact during the period of change;
• Statements or admissions by the alleged influencer, texts, emails, or recordings that show pressure, threats, or explicit instructions;
• Financial records showing suspicious transfers, gifts, or sudden access to the testator’s funds by the beneficiary;
• Witness accounts that the testator seemed frightened, confused, or unable to act freely at the time of execution.

Formalities and procedural rules to watch

Washington law requires certain formalities for a will to be valid. If a will fails to meet these formalities it may be easier to challenge.

• Written will, signature, and attestation by two competent witnesses are generally required. See RCW 11.12.010 and RCW 11.12.020 for statutory execution rules: RCW 11.12.010 and RCW 11.12.020.
• If formalities are defective, courts may still admit other proof in narrow circumstances (for example, holographic wills or proof under statutory exceptions); consult an attorney about your situation.

How courts weigh evidence

Court decisions look at the whole factual picture. A single piece of evidence rarely wins a contest by itself. Courts consider timing (how soon after the challenged event the evidence was created), consistency across sources, and whether independent witnesses or medical professionals corroborate claims. Challengers typically must present persuasive proof; Washington courts give weight to contemporaneous medical and witness evidence.

Practical steps to gather and preserve evidence

1. Obtain medical records and physician notes for the period around the will signing. Healthcare providers often keep useful contemporaneous records.
2. Collect communications — emails, texts, voicemail, letters — involving the testator and potential influencers or beneficiaries.
3. Identify and record contact information for witnesses who saw the testator in the weeks before and at the signing.
4. Preserve financial records and bank activity that show transfers, unusual withdrawals, or changes in account access.
5. Secure copies of all will drafts, appointment logs (appointments with attorney), and notary/witness forms if available.
6. Do not destroy evidence or coach witnesses. Follow proper legal process — spoliation can hurt your case.
7. Talk to an attorney quickly. Evidence can disappear or memories fade; lawyers can help issue subpoenas and collect documents lawfully.

Timing and procedural notes

Will contests have deadlines. If a will has been submitted for probate, you typically have a limited window to file a contest. Consult local court rules or an attorney to learn the exact deadlines and procedures in the county where probate is filed.

Helpful Hints

• Start collecting evidence immediately — medical records and witness memories are most accurate close in time to the event.
• Preserve originals when possible (original will, dated drafts, signed statements). Make certified copies of documents and keep a chain of custody log.
• Look for multiple independent sources that point to the same conclusion (medical notes + witness testimony + financial records strengthen a claim).
• Document who had access to the testator and when — caregivers, family members, and others who controlled appointments or finances.
• If you can, obtain neutral expert evaluations (neuropsychological testing or geriatric psychiatry) to support claims about capacity.
• Be cautious about recordings — Washington is a two-party consent state for some recordings. Obtain lawful evidence and ask an attorney if you’re unsure about admissibility.
• When in doubt, consult a Washington probate/estate attorney quickly to preserve rights and meet local filing deadlines.

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