A will is a document that states an individual's wishes once he or she has passed away. It is seen by the courts as the voice of the person who wrote the will. This person is known as the testator. Although it is considered difficult for someone to challenge a will, there are certain circumstances that may allow someone to successfully do so.
First, the person that wishes to challenge the will typically has an interest to gain from the will itself. As an example, the person challenging the will would generally be a spouse or other family member who believes he or she should have been included in the will and was left out, or that he or she should have received something other than what the testator left for him or her.
Second, there must be grounds for the person to challenge the will. They would need to show that the person who wrote the will did not have testamentary capacity or rather, was not of sound mind when he or she made the will. They could also challenge the will based on the fact they believe the person was unduly influenced by someone so that he or she would make out the will in a certain way. As an example, a family member, such as a son or daughter could persuade the person to leave a larger part of his or her inheritance than was left to a sibling.
Since adults are generally presumed to be of sound mind or have testamentary capacity when they make out a will, when a challenge arises, it is generally made on the basis that the adult had a mental incapacity, such as dementia, senility, or insanity that made him or her unaware of the consequences those decisions would have when the will was made. In the event the person is able to show this, the court may then void the will in its entirety or only certain parts.
Individuals who are involved in legal disputes involving challenging a will may find it beneficial to seek counsel with an experienced California attorney.
Source: FindLaw, "Reasons to Challenge a Will" accessed Jan. 30, 2015