Challenging a will: testamentary capacity, evidence and assessment by a lawyer

1. Identify the will and the problem you mean

Gather the relevant text, date and notary's details. An old family document is not automatically the will requiring assessment at death. If necessary, first request a notarial investigation into the registered instrument. Then write down which provision affects your interest and the specific defect you suspect. Dissatisfaction with the financial result is different from the legal validity of how the will was made.

A lawyer can help distinguish interpreting words, assessing validity and a separate monetary entitlement. Those questions may coexist, but require different evidence and claims. A letter merely saying you disagree with everything does not yet identify what a court should decide. Begin with the specific instrument and the result you seek.

2. Assess testamentary capacity around the relevant decision

Notaris.nl explains that the notary checks whether someone can decide independently and understand the consequences. Capacity is linked to the act and circumstances. According to that explanation, a dementia diagnosis does not immediately mean someone can no longer make any will. One moment or decision may differ from another. Advanced age or physical vulnerability alone therefore does not determine the question.

Prepare a chronology around discussion and signing of the instrument. Record concrete observations, who was present and which source supports the date. A memory of confusion years earlier may say something different from information from the relevant period. Include facts that do not support your suspicion too. Focused advice requires a complete file, not a selection omitting every unfavourable indication.

The civil-law test for a mental disorder follows from Article 3:34 of the Dutch Civil Code: did the disorder prevent a reasonable appraisal of the interests involved, or was the declaration made under its influence? For a will, as a unilateral legal act not addressed to specified persons, absence of will may result in nullity. The relevant disorder and its connection to the declaration must be legally substantiated. The care taken in the notary's investigation and this civil validity question are not the same assessment.

3. Distinguish independent decision-making from an unproven family accusation

The notary's examination also considers whether a person forms their wishes freely and independently. A relative arranging transport or attending an initial contact does not automatically prove improper influence. Describe who contacted the office, who gave instructions and which specific events worry you. Put facts and your interpretation in separate columns.

The KNB discusses a disciplinary case in which certain warning signs required more careful investigation; in another disciplinary decision read, the complaint was instead dismissed after assessment of the conversations. Such cases do not predict the outcome of your file. They show that context and actual working methods matter. Have a lawyer assess the possible legal significance of your facts without presenting every conflict as proof of influence.

Not every form of influence provides civil grounds for annulment. Article 4:43(1) excludes annulment of a testamentary disposition on the ground of abuse of circumstances. Other grounds, such as threats, fraud or an incorrect motive, have their own rules; for the latter, relevant requirements include the supposed circumstance being stated in the will and its decisive character. Have the particular ground distinguished from a disciplinary allegation against the notary.

4. Gather evidence through lawful, targeted requests

Bring together existing letters, relevant messages and names of potential witnesses. Describe what each source may support and whether it concerns direct observation or information passed on by others. A pile of emotional family messages does not automatically establish mental condition when the will was executed. Ask the lawyer what further investigation is worthwhile and which information is still missing for an initial assessment.

Access to notarial and medical information is not unlimited. Do not assume that, as a relative, you can demand every file or use passwords to search for information. Have lawful access or evidential routes assessed. In discussing an investigation during life, Notaris.nl states that assistance from an independent doctor requires consent. This underscores why privacy and access are separate legal questions, even when your concern is genuine.

5. Keep a complaint separate from a dispute about the will

A notarial disciplinary complaint concerns the notary's professional conduct. The decision read from 2025 explains that the disciplinary court assesses, among other things, compliance with the Civil-Law Notaries Act and professional care. Civil proceedings about the will pursue a different aim. Do not assume that filing a complaint immediately disapplies the will or blocks distribution.

The same applies to an upheld complaint: have its consequences for your property-law position assessed separately. A lawyer can explain which path can actually serve your aim and which deadlines apply. Also ask whether other rights need protection meanwhile. A possible reserved-share claim may need separate attention and does not automatically wait for the outcome of a complaint or investigation into the instrument.

6. Discuss standing, costs and necessary first steps

Have it assessed what difference a successful challenge would make for you. An earlier will or statutory succession may become relevant, but the outcome is not established simply by disputing the latest document. Bring older known documents and family information too. Request a scenario analysis with uncertainties rather than only a general opinion that the will is strange.

Agree the cost of an initial file assessment and what additional investigation is being considered. Ask which action is necessary now and what can wait. An impending sale or payment may require urgent advice, but not every disagreement automatically justifies interim relief. The lawyer must assess the actual interest and appropriate procedure. Do not commit to pursuing a costly course in full before the engagement and evidential position are clear.

7. Fictional example: a diagnosis after a change to a will

Suppose a parent changes a will and later receives a dementia diagnosis. A child receiving less concludes that the instrument must therefore be invalid. The later diagnosis may prompt questions, but does not independently establish the condition at the relevant decision. The timeline, concrete observations and notarial investigation matter for that assessment.

The child therefore gathers documents from the right period and asks a lawyer which assessment and evidential route are possible. Separate entitlements and deadlines are examined at the same time. This fictional example does not say whether the parent did or did not have capacity then. It shows why a medical label and an unwanted financial outcome do not replace legal and factual investigation of the file.

8. Checklist for the initial inheritance-law assessment

Give the lawyer facts both supporting and contradicting your suspicion. State what you want to achieve and which action you think cannot wait. Make every evidence source traceable to an event around the relevant instrument.

• Disputed will, date, notary's details and available earlier wills.
• Family information and explanation of your own interest affected by the provision.
• Chronology of health and concrete observations around discussion and signing.
• Relevant correspondence, potential witnesses and the origin of information already available.
• Earlier complaints or agreements, announced administration acts and separate claim deadlines.