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Irrational hostility and insane delusion – two unusual grounds to challenge a the validity of a Will

A case study

The Claimant, an only child, instructed us to bring a claim against the legal validity of his deceased mother’s last Will under which he was not a named beneficiary. Instead the entirety of her estate had been left to a friend. The deceased’s Will file provided detailed reasons for disinheriting our client including a signed statement strongly suggesting she was either suffering from an insane delusion directing her decision to disinherit our client at the time and/or because her natural affection for her son (our client) had been poisoned by a disorder of her mind.

Why did we believe the deceased had been suffering from an insane delusion and/or that her natural affection for her only child had been poisoned?

Firstly, she believed she had already given her late husband’s estate to our client. This was manifestly incorrect. Our client could prove from his bank statements that he received no money from his mother at all at the time his father’s estate was administered and/or shortly thereafter and never in the sums that his father left when he passed away.

Secondly, the statement explaining her reasons for disinheriting our client (her only child as mentioned) also revealed a very strong animosity towards him which had no foundation whatsoever; the same irrational animosity towards others who were close to the deceased and/or who tried to help her was also regularly recorded in her medical records.

Lack of legal testamentary capacity – insane delusion and irrational hostility

The legal test for “capacity” to make a Will is provided in Banks v Goodfellow:

This includes the explanation or definition of the legal test for capacity as follows: where the test for capacity was stated by Cockburn CJ:

It is essential to the exercise of such a power (of making a will) that a testator shall understand the nature of the act and its effects; shall understand the extent of the property of which he is disposing; shall be able to comprehend and appreciate the claims to which he ought to give effect; and, with a view to the latter object, that no disorder of the mind shall poison his affections, pervert his sense of right or prevent the exercise of his natural faculties – that no insane delusion shall influence his will in disposing of his property and bring about a disposal of it which, if the mind had been sound, would not have been made. Here, then, we have the measure of the degree of mental power which should be insisted on. If the human instincts and affections, or the moral sense, become perverted by mental disease; if insane suspicion, or aversion, take the place of natural affection; if reason and judgment are lost, and the mind becomes a pray to insane delusions calculated to interfere with and disturb its function, and to lead to a testamentary disposition, due only to their baneful influence – in such a case it is obvious that the condition of the testamentary power fails, and that a will made under such circumstances ought not to stand.’

Insane delusion – Loss of mental capacity is not a prerequisite

It does not appear to be the case that a finding of loss of mental capacity has to be made to prove this type of case. In the more recent case of Clitheroe v Bond [2021] EWHC 1102 (Ch)

it was found that there was no suggestion of cognitive impairment (paragraph 22) and yet notwithstanding the Deputy Master at first instance found her last two Wills to be invalid because she lacked legal testamentary capacity, seemingly upheld on appeal to Mrs Justice Falk, who also provided a valuable commentary on the nature and application of “insane delusions” to a case of this nature. For example:

(from paragraphs 106 to 107 – the definition of an “insane delusion”)

One question that arises is the precise relevance of the medical definition of “delusion” to the legal test of testamentary capacity. This was not the subject of specific submissions so I limit myself to a few observations. First, the Banks test of incapacity must not be understood as being limited to incapacity caused or manifested by a “delusion” as now clinically understood. A far broader category of disorders may result in incapacity, and the 19th century cases need to be considered with that in mind. Secondly, the list of disorders is not necessarily closed. Key v Key provides an example of testamentary capacity being found to be lacking as a result of the effect of bereavement, both experts in that case having accepted that bereavement could cause an affective disorder (see paragraph [95] of that decision). Thirdly, Professor Jacoby’s evidence was that a delusion requires a disorder of the mind, that is some form of mental illness (see [94] above). Dr Series confirmed at the trial that he largely agreed with Professor Jacoby’s evidence on this issue, and he also specifically confirmed that there are “delusional disorders for which the evidence of mental disorder is only the delusion”. In addition he stated that if Jean had a delusion then it was “very possible that that was related to an affective disorder” (see [93] above).

107. Put another way, as I understand the expert evidence a delusion (in the clinical sense) is not itself a medical disorder, although it may be evidence of one. In this case, and as discussed further below, the Deputy Master’s conclusion was that Jean was suffering from an affective disorder.

(paragraph 153(b) – establishing whether a “delusion” exists)

b) In order to establish whether a delusion exists, the relevant false belief must be irrational and fixed in nature. It not an essential part of the test that it is demonstrated that it would have been impossible to reason the relevant individual out of the belief if the requisite fixed nature can be demonstrated in another way, for example by showing that the belief was formed and maintained in the face of clear evidence to the contrary of which the individual was aware and would not have forgotten.

The testator in our case hadn’t apparently lost her mind completely and/or it appeared that she retained capacity in relation to her every day affairs. There was sufficient evidence of an insane delusion because her belief that she had already gifted her late husband’s estate to our client was fixed but also false.

Irrational hostility

It would appear that this needs to be linked to a “disorder of the mind” (as per Banks v Goodfellow above –  “that no disorder of the mind shall poison his affections, pervert his sense of right or prevent the exercise of his natural faculties”). As mentioned, the medical records confirmed that the deceased exhibited irrational hostility and aggression towards not only her son (our client) but others and further that this was strongly associated with her depression and alcoholism both of which are “disorders of the mind”. There was no obvious basis for her hostility towards any individual but in particular to our client except that it was directed towards those to whom she appeared to have the closest ties. Again then there was a potential case which was revealed by reference to the papers – here, the deceased’s medical records.


The claim was compromised. The estate was relatively modest and certainly too small for either side to contemplate a trial.

If you believe that you might have grounds to contest a will, it’s important to get in touch with a professional who can help you through this challenging time and support you legally. At Will Claim Solicitors, we specialise in assisting our clients in contesting wills for estates most commonly based in England and Wales. Our expert solicitors are on hand to support you on a ‘no win, no fee’ basis, so get in touch to arrange your free claim assessment here