What Is Undue Influence When Challenging a Will?

Written by Tanya Waterworth, Digital Content Writer

About Our Legal Expert: This content is produced with oversight by Michael Jefferies, Managing Director who has over 30 years’ legal experience.

A Practical Guide to Proving Coercion and Building a Strong Claim

When concerns arise that a will does not reflect the true wishes of the person who made it, the most common question is what is undue influence when challenging a will? This is one of the most difficult grounds to investigate. Unlike lack of capacity, which focuses on a person’s mental ability, undue influence centres on whether someone else overpowered the testator’s free will.

So, we look at practical realities of proving undue influence, including how courts assess dependency, what evidence carries weight, and the strategies which can strengthen a claim. However, if you’re unsure whether the issue is capacity or influence, see our overview of grounds to challenge a will.

We partner with experienced contentious probate solicitors who offer a range of fee structures, including ‘No Win, No Fee’ for certain cases along with other flexible funding and a free, initial consultation – speak to our team to find out more.

Understanding Undue Influence in Will Disputes

Undue influence arises when pressure, manipulation, or coercion causes a testator to make decisions they would not have made freely. Because this behaviour often happens privately, proving it requires a careful, evidence‑based approach.

Courts look at the overall pattern of behaviour, the testator’s vulnerability, and the influencer’s opportunity to exert control. The question is not simply whether influence existed as influence is common in families – but whether it crossed the line into coercion.

How Courts Evaluate Dependency and Vulnerability

A central part of any undue influence claim is showing that the testator was susceptible to being influenced. Courts examine the nature of the relationship between the testator and the alleged influencer, paying close attention to:

1. Physical or Cognitive Weakness

• Illness, frailty, mobility issues
• Cognitive decline or confusion
• Reliance on others for daily tasks

These factors do not automatically prove undue influence, but they increase the likelihood that pressure could be effective.

2. Emotional or Social Dependence

Courts consider whether the testator:

• Relied heavily on one person for companionship
• Was isolated from other family members
• Trusted the influencer to manage personal or financial affairs

A relationship of dependency does not invalidate a will on its own, but it provides important context for assessing whether influence was improperly exerted.

3. Control Over Access

If the alleged influencer restricted who could visit, speak to, or advise the testator, this can be a significant red flag. Courts closely examine at:

• Gatekeeping behaviour
• Sudden changes in who the testator interacts with
• Attempts to exclude professionals or family members

Patterns of isolation often form part of the evidential picture.

4. Burden of Proof in Undue Influence Claims

The burden of proof typically lies with the person challenging the will. Because undue influence is rarely witnessed directly, courts accept that evidence may  often be circumstantial. However, it must still be compelling.

To meet the burden of proof, claimants must demonstrate that:

• The testator was vulnerable
• The alleged influencer had the opportunity to exert pressure
• The resulting will is inconsistent with the testator’s usual intentions
• The surrounding circumstances are suspicious or abnormal

Courts assess the totality of the evidence, not isolated incidents.

Strategies for Strengthening an Undue Influence Claim

Building a persuasive case requires a structured approach. The following strategies can significantly improve the chances of success:

1. Document Patterns, Not Just Events

Isolated incidents rarely prove undue influence. Courts look for:

• Repeated controlling behaviour
• Ongoing pressure or manipulation
• A consistent pattern of dependency or isolation

Keeping a detailed timeline can be invaluable.

2. Highlight Changes From Long‑Standing Intentions

Evidence that the will:

• Suddenly excludes close family
• Makes disproportionate gifts
• Conflicts with previous wills can help demonstrate that the testator’s free will was overridden.

3. Show How the Influencer Benefitted

If the alleged influencer receives a substantial or unexpected benefit, this can support the argument that pressure was applied.

Expert Evidence: How Professionals Strengthen a Claim

Expert evidence is often crucial in undue influence cases, especially when the testator’s vulnerability is in question. We partner with contentious probate solicitors who can help to gather evidence from:

1. Medical Experts

Doctors, psychiatrists, or geriatric specialists who can provide insight into:

• Cognitive functioning
• Susceptibility to pressure
• Whether illness or medication affected decision‑making

Their assessments help establish whether the testator was capable of resisting influence.

2. Psychological or Behavioural Experts

These experts may comment on:

• Dependency dynamics
• Personality traits that increase vulnerability
• The psychological impact of isolation or coercion

Their analysis can help explain why the testator may have complied with pressure.

3. Handwriting or Document Experts

While not directly related to influence, they can:

• Verify signatures
• Identify unusual drafting circumstances
• Support claims of suspicious behaviour around the will’s preparation

Expert evidence is not compulsory, but it often strengthens the narrative and helps courts understand the broader context of what was happening.

Recognising Warning Signs of Undue Influence

Although each case is unique, common indicators include:

• Last‑minute changes benefitting one individual
• Isolation from friends, relatives, or advisers
• Uncharacteristic decisions or behaviour
• Heavy reliance on a single caregiver or acquaintance
• Pressure, threats, or emotional manipulation

These signs should prompt further investigation, especially when combined with dependency or vulnerability.

Contact Us Today

Challenging a will on the grounds of undue influence is a complex but vital process to ensure the testator’s true intentions are honoured. Recognising the signs of manipulation, understanding the legal framework, and taking prompt, evidence-based action are essential for success.

If you suspect a will may have been influenced improperly, get in touch with us today.

Contact our friendly team on 0333 358 3034 or complete our online contact form to arrange an initial, no-obligation telephone consultation.