Q: Can a will be set aside if the testator lacked the mental capacity to create a will?
According to CEB’s California Trust and Probate Litigation, one of the grounds for contesting a will is that the testator lacked the requisite mental capacity at the time the will was executed. Under Probate Code §6100.5(a), a person is mentally incompetent to make a will, if at the time of making the will, he or she did not have sufficient mental capacity:
1. To understand the nature of the testamentary act;
2. Understand and recollect the nature and situation of his or her property;
3. Remember and understand his/her relations to living descendants, spouse, parents, and others whose interests are affected by the will; or
4. Suffers from a mental disorder with symptoms including delusions or hallucinations that result in devising the property in a way she/he would not have if not for the delusions or hallucinations.
Besides researching case law and the standards under Probate Code §6100.5(a), you should also research the Due Process in Competence Determinations Act, Probate Code §§810-813, which provides the statutory framework for making determinations on competency.
Please note this is a starting point to research setting aside a will based upon lack of capacity. You may have to do further research.
Disclaimer: For this question, I researched one resource but we may have other materials in the library that provide the same information or additional information not covered in the resource used. Please note that the answers to these questions are not meant to be all-encompassing or to cover every nuance or exception that may apply. It is simply a starting point for you to conduct your own research.