What condition may cause a will to be considered invalid?

A will may be considered invalid if the testator lacks testamentary capacity. This condition refers to the mental ability of an individual, at the time of making the will, to understand the nature and extent of their property, the Act of making a will, and the implications of distributing their assets through that will. If a testator does not possess this capacity due to reasons such as mental illness, significant impairment, or being under the influence of substances, the will may be challenged and deemed invalid in a court of law.

In contrast, the absence of a signature from the executor, while it might cause practical issues in administering the will, does not inherently invalidate the document itself. A witness signing not under oath does not affect the validity of the will, as witnessing requirements can vary significantly by jurisdiction and may not always require an oath to be valid. Furthermore, failing to list all assets in the will does not invalidate the will; it may simply lead to the application of intestacy laws for any assets not mentioned, rather than affecting the overall validity of the testamentary document.