A holographic will is a handwritten will.
A holographic will is one in which the substantive terms are in the handwriting of the testator and it is signed by him or her without the usual 2 witnesses. Until about 25 years ago most states refused to honor these since they were not witnessed. But the Uniform Probate Code which was adopted in various forms
by almost all states now recognizes these as valid, however there has to be testimony in open court by someone who is familiar with the handwriting and signature of the decedent and that the will is in the decedent's handwriting and the signature is the decedent's. Usually such testimony is given by a close family member or friend. Usually a handwriting expert is not needed unless someone contests the will.