It is possible, but difficult. 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: (1) the will was not properly signed; (2) the person making the will (the "testator") lacked the requisite testamentary capacity; (3) the testator was subjected to undue influence in the making of the will; (4) the testator was fraudulently induced into signing the will; and (5) there was a mistake in the will.
Sometimes expert testimony is required. For example, the contestant might need a psychiastrist to review the decedent's medical records to provide an opinion on the mental capacity at the time the will was signed.