Will Contested for Undue Influence or Lack of Capacity in ACT - Legal Options

By James Stevens, Director and Solicitor, Go To Court Lawyers. Last reviewed 10 April 2026.

Will disputes based on undue influence or lack of testamentary capacity challenge the validity of a will itself, claiming the deceased was either manipulated or mentally incapable when making their will. These claims are heard in the ACT Supreme Court and require strong medical and witness evidence to succeed. Unlike family provision claims that seek a larger share of an estate, these disputes can invalidate an entire will, potentially reverting the estate to an earlier will or intestacy rules. Time limits apply strictly - you must act within 6 months of probate being granted or risk losing your right to contest.

Do You Need a Lawyer?

Yes, you absolutely need specialist legal representation for will validity challenges in the ACT Supreme Court. These cases require complex medical evidence, expert witnesses, and detailed knowledge of testamentary capacity law that self-represented litigants cannot navigate effectively. Without proper legal help, you risk having your case dismissed on procedural grounds before the evidence is even considered.

The stakes are enormous - a successful undue influence or lack of capacity claim can invalidate an entire will worth hundreds of thousands or millions of dollars. However, an unsuccessful challenge can result in you paying the other side's legal costs, potentially reaching $50,000 to $200,000 or more. Courts take a dim view of weak challenges and will order indemnity costs against unsuccessful applicants who cannot prove their case.

What a lawyer can change: Proper legal representation means gathering the right medical evidence, interviewing key witnesses before memories fade, obtaining expert psychiatric assessments, and presenting your case according to strict Supreme Court procedures. Many valid claims fail simply because families attempt to handle complex litigation themselves.

What Happens Next - The Process

1. Urgent evidence gathering (first 30 days): Contact the deceased's doctors, obtain medical records, interview witnesses who observed the deceased's mental state or interactions with beneficiaries around the time the will was made.
2. File caveat at ACT Supreme Court: Lodge a caveat to prevent probate being granted while you investigate. This costs approximately $100 and gives you time to build your case.
3. Obtain expert medical opinion: Engage a psychiatrist or geriatrician to review medical records and provide an expert report on testamentary capacity or susceptibility to influence.
4. File originating application: Submit your formal challenge to the ACT Supreme Court within 6 months of probate being granted, including all supporting affidavits and medical evidence.
5. Discovery and evidence phase (3-6 months): Exchange documents with other parties, take witness statements, potentially conduct medical examinations of key witnesses.
6. Mediation attempt: Court-ordered mediation to explore settlement, which occurs in approximately 70% of will dispute cases to avoid trial costs.
7. Supreme Court trial: If settlement fails, a judge-only trial where medical experts testify and witnesses are cross-examined about the deceased's mental state and circumstances surrounding the will.
8. Judgment and costs orders: Court determines will validity and makes orders about who pays legal costs, which can exceed the value of disputed assets.

Each step has strict deadlines that can destroy your case if missed. The ACT Supreme Court does not grant extensions for procedural failures by unrepresented parties.

The Law in Australian Capital Territory

Will disputes in the ACT are governed by the Wills Act 1968 (ACT) and general common law principles around testamentary capacity and undue influence. The ACT Supreme Court has exclusive jurisdiction over will validity challenges.

Testamentary capacity requirements: Under Banks v Goodfellow (1870), the deceased must have understood: (1) the nature of making a will, (2) the extent of their property, (3) the claims of people who might expect to benefit, and (4) how these factors relate to each other. Mental illness alone does not invalidate a will - the question is whether the specific illness affected these four areas of understanding.

Undue influence definition: The deceased's will must have been overcome by pressure that destroyed their free will. Courts require proof of: (1) the deceased was susceptible to influence, (2) the beneficiary had opportunity to exercise influence, (3) the beneficiary had a disposition to influence, and (4) the will shows the influence was actually exercised.

Time limits: Section 18 of the Administration and Probate Act 1929 (ACT) requires will challenges within 6 months of probate being granted. Extensions are rarely granted and require exceptional circumstances.

Costs exposure: Under ACT Supreme Court Rules, unsuccessful applicants typically pay the other side's legal costs. In cases involving unreasonable conduct, courts can order indemnity costs at approximately 30% higher than standard costs.

Mistakes to Avoid

1. Waiting too long to gather medical evidence: Doctors' memories fade rapidly, and medical records become harder to obtain after 12 months. We see families lose winnable cases because they spent months grieving instead of immediately securing evidence about the deceased's mental state and medication effects.

2. Confusing undue influence with family pressure: Normal family discussions about inheritance, even heated ones, do not constitute undue influence. Courts require evidence that the deceased's free will was completely overcome - not just that they were persuaded or argued with. Many families waste tens of thousands pursuing weak undue influence claims based on ordinary family dynamics.

3. Assuming mental illness equals lack of capacity: Depression, mild dementia, or even psychiatric hospitalisation does not automatically invalidate a will. Courts focus on whether the specific condition affected the deceased's understanding of their will at the exact time they signed it. We regularly see families shocked when judges uphold wills made by people with diagnosed mental health conditions.

4. Filing without proper medical expert reports: ACT Supreme Court judges will not accept family observations about the deceased's mental state without supporting expert psychiatric or geriatric evidence. Cases collapse when families rely on their own opinions rather than qualified medical testimony.

5. Underestimating costs exposure: Failed will challenges can result in cost orders exceeding $100,000 against unsuccessful applicants. Many families remortgage homes or exhaust savings pursuing cases without realistic prospects, then face devastating cost orders that destroy their financial security.

Likely Outcomes and Costs

Success rates: Approximately 25% of will validity challenges succeed at trial, though 70% settle before reaching court. Lack of capacity claims have higher success rates than undue influence claims, which require proving someone deliberately manipulated the deceased.

With proper legal representation: Experienced lawyers can assess your prospects honestly within the first consultation, preventing you from pursuing hopeless cases. Strong cases often settle for 60-80% of claimed amounts, avoiding trial risks and costs. Weak cases get discontinued early, minimising costs exposure.

Going alone risks: Self-represented litigants face immediate dismissal for procedural failures, cannot effectively cross-examine expert witnesses, and routinely receive adverse costs orders. ACT Supreme Court statistics show unrepresented parties lose over 85% of contested will cases.

Legal costs: Expect $25,000 to $75,000 for cases that settle at mediation. Trial costs range from $80,000 to $250,000 depending on complexity. However, successful challenges can recover estates worth $500,000 to several million dollars.

Timeframes: Simple cases resolve within 8-12 months. Complex matters involving multiple medical experts can take 18-24 months. The ACT Supreme Court prioritises estate matters, so delays usually result from gathering evidence rather than court availability.

Family provision combinations: Many clients run alternative claims - challenging will validity while seeking family provision as backup. This strategy costs approximately 30% more but protects against total failure if the will validity challenge fails.

How Go To Court Lawyers Can Help

Go To Court Lawyers has represented hundreds of families in ACT will disputes since 2010, with specialist estate litigation lawyers who understand the medical evidence and expert witnesses needed to win these complex cases. Our ACT team knows every Supreme Court judge's preferences and the local medical experts courts respect.

What makes us different: We work with the same psychiatric and geriatric experts regularly, understand which medical evidence persuades ACT judges, and can assess your case prospects honestly in the first meeting. Our 800+ lawyers nationally mean we handle estate disputes across multiple states when families have assets everywhere.

Fixed-fee consultation: Meet with specialist estate lawyers who will review your evidence, explain realistic prospects, and provide written advice about costs and timeframes. No surprises, no pressure - just honest assessment of whether you have a case worth pursuing.

24/7 availability: Call 1800 577 015 any time for urgent will dispute advice. Time limits are strict, and evidence gathering cannot wait. Our emergency hotline connects you to lawyers who handle estate litigation daily.

Proven results: 4.5-star rating from 780+ client reviews, with testimonials specifically praising our estate dispute outcomes and cost transparency. We win cases other firms reject and settle matters other lawyers take to expensive trials.

Don't risk representing yourself in ACT Supreme Court or missing crucial evidence gathering deadlines. Book your fixed-price consultation online at gotocourt.com.au/book or call 1800 577 015 now. Evening and weekend appointments available for families dealing with urgent probate deadlines.