How Does Mental Illness Affect the Capacity to Make a Will?

Great strides have been made in recent times toward finding a cure for dementia and Alzheimer's disease, but it remains a scourge of Australian society. Many people who reach advanced age find it increasingly difficult to make decisions on their own behalf and this can be particularly problematic when it comes to designing a will. If you suspect that a loved one was incapacitated in this extent and are not sure about the legality of the will, what can you do?


A will allows an individual to leave all their property and possessions to specific people or organisations, when they depart this world. For this to be effective, however, they need to have "freedom of testamentary disposition," which is a legal term describing their mental capacity. It's possible to bring this into question if there is a dispute due to dementia or other illness and to ask whether the document is legally binding.

Professional Opinion

To make a determination, a senior doctor will be brought in who has experience in this area. They will be presented with all the information relative to the case, so that they can check and provide their professional opinion. They will want to know if the person signing the document fully understood exactly what the document related to. Also, they need to convince themselves that the individual knew how valuable the property in question was and to whom they were leaving it. 


Sometimes, these illnesses can present considerable difficulty when it comes to identifying family members, friends or others who might be expected to benefit. Not only that, but some people with less-than-honourable intentions may try to take advantage of the situation and convince the individual that they should be a beneficiary in some way.

It's very important for relatives who are looking after the ailing person to protect them and keep them away from people with such motives. Some of these criminals can be very persuasive and may convince the individual that they represent a very good cause. Sometimes, they can even persuade them to create a brand-new will, naming them or their organisation as the sole beneficiary.

Looking at Previous Versions

It's not unusual for anyone to create a number of different wills as the years go by and if one is challenged based on a lack of testamentary capacity, then there's no reason why a previous one may not still be valid. Of course, similar questions may be asked and it will be important to determine that they were not inflicted by this illness back then.

Getting Assistance

This can be a complicated subject and difficult to prove either way, so it is important to get the help of a competent lawyer.