Lack of valid execution
Under the Wills Act 1837, a will must comply with certain formalities and the correct procedure must be followed when it is being signed and formalised. If the Last will and testament has not been made properly this can lead to it being rendered invalid. For example, if witnesses were not present when the person making the will (ie the testator) signed their will, it can be challenged.
Lack of testamentary capacity
With people living longer and dementia on the rise, there is more potential for a will to be challenged on the grounds that the testator lacked 'mental capacity' when writing their will. Lacking mental capacity is defined, under the Mental Capacity Act 2005, as the inability for someone to make a decision for themselves due to an impairment of the brain. This can apply to dementia, brain injury and certain mental illnesses.
In deciding whether the testator lacked mental capacity, the courts especially consider their medical records and the opinion of a suitably qualified medical expert.
Lack of knowledge or approval, forgery and fraud
If a will has been drawn up by a third party, and the testator signs the will without full awareness or understanding of its contents, it can be deemed invalid. Examples include the deceased testator:
having a low level of literacy
being frail, unwell or otherwise vulnerable and the will being particularly complex or unusual
having a visual impairment
appearing to have directed someone else to sign the will
Similarly, if a will is forged or has been affected by fraudulent statements, this will no longer constitute an enforceable legal document.
If the testator was coerced to draft their will in a certain way or made changes to their will under duress, this can lead to it being rendered invalid. However, this type of claim can be difficult to prove.
Inheritance Act 1975
Even if there is no challenge to the validity of a will, it can still be contested under the Inheritance (Provision for Family and Dependants) Act 1975. This allows dependents of the deceased (including cohabitees) to make a claim against the estate if they can prove that they were financially dependent on the deceased and were not sufficiently provided for in the will.