Wills and trusts can be contested on a variety of grounds. The administration process can also be disputed by involved parties who believe their rights have been disregarded. Fiduciaries and administrators can have their performance challenged, and beneficiaries can sue for increased inheritances, including a spouse's right of election. These are serious legal matters, and parties involved in estate litigation need legal assistance and guidance to prosecute or defend against these claims.

A will contest is a court proceeding in which a court is called upon to determine the validity of a will. The person challenging the validity of a will is often referred to as the "contestant." The person who is defending the will is called the "proponent."

In a will contest, the contestant offers proof or evidence that the will is invalid. Such proof is usually intended to demonstrate any one or more of the following:

• The will was not properly executed - Proper execution of a will requires that the will be signed by the testator (the person making out the will) and witnessed by at least two people, who also sign the will at the end. A will can be contested on the grounds that it was not properly drafted, signed, or witnessed in accordance with statutory legal requirements. A will can also be contested on the grounds that there are ambiguities in the document. When a will is executed under the supervision of an attorney, there is a presumption that it was properly executed.
  
  

  CA Probate Code §6110 (a) Except as provided in this part, a will shall be in writing and satisfy the requirements of this section. (b) The will shall be signed by one of the following: (1) By the testator. (2) In the testator's name by some other person in the testator's presence and by the testator's direction. (3) By a conservator pursuant to a court order to make a will under Section 2580. (c) The will shall be witnessed by being signed by at least two persons each of whom (1) being present at the same time, witnessed either the signing of the will or the testator's acknowledgment of the signature or of the will and (2) understand that the instrument they sign is the testator's will.

  
  

• The testator was not mentally competent to make a will - Competency to make a will means that the testator understood the nature and extent of his assets and knew the parties to whom the assets would be distributed. A will may be declared void if it can be proved that the testator was senile, delusional or of unsound mind when the will was created. Incompetence may be proven by medical records, irrational conduct of the testator and the testimony of those who observed him/her at the time the will was executed.
  
  

  CA Probate Code §6100.5 (a) An individual is not mentally competent to make a will if at the time of making the will either of the following is true: (1) The individual does not have sufficient mental capacity to be able to (A) understand the nature of the testamentary act, (B) understand and recollect the nature and situation of the individual's property, or (C) remember and understand the individual's relations to living descendants, spouse, and parents, and those whose interests are affected by the will. (2) The individual suffers from a mental disorder with symptoms including delusions or hallucinations, which delusions or hallucinations result in the individual's devising property in a way which, except for the existence of the delusions or hallucinations, the individual would not have done. (b) Nothing in this section supersedes existing law relating to the admissibility of evidence to prove the existence of mental incompetence or mental disorders. (c) Notwithstanding subdivision (a), a conservator may make a will on behalf of a conservatee if the conservator has been so authorized by a court order pursuant to Section 2580.

• The will was the product of fraud or undue influence - Undue influence occurs when the testator is compelled or coerced to execute the will as a result of improper pressure exerted upon him/her. Fraud occurs when a false statement is knowingly made causing the testator to sign a will in a different manner than he/she would have if the statement had not been made.
  

• A second will is discovered - If proven valid, the newer will would replace the older will.
  
  

  CA Probate Code §6104 The execution or revocation of a will or a part of a will is ineffective to the extent the execution or revocation was procured by duress, menace, fraud, or undue influence.

  
  

• Miscellaneous reasons - There are other circumstances under which a will can be contested. These include suspicions of forgery and the existence of pre-existing contracts relating to asset distribution.
  
  

  CA Probate Code §6111 (a) A will that does not comply with Section 6110 is valid as a holographic will, whether or not witnessed, if the signature and the material provisions are in the handwriting of the testator. (b) If a holographic will does not contain a statement as to the date of its execution and: (1) If the omission results in doubt as to whether its provisions or the inconsistent provisions of another will are controlling, the holographic will is invalid to the extent of the inconsistency unless the time of its execution is established to be after the date of execution of the other will. (2) If it is established that the testator lacked testamentary capacity at any time during which the will might have been executed, the will is invalid unless it is established that it was executed at a time when the testator had testamentary capacity. (c) Any statement of testamentary intent contained in a holographic will may be set forth either in the testator's own handwriting or as part of a commercially printed form will.

• Incorrect Interpretation - There may exist a difference of opinion regarding the testator's words or intent in the formation of the Will.
  
  

  CA Probate Code §6111.5 Extrinsic evidence is admissible to determine whether a document constitutes a will pursuant to Section 6110 or 6111, or to determine the meaning of a will or a portion of a will if the meaning is unclear.