(a) If a witness to a will or other party who shall testify to have a will admitted (1) is dead, (2) is blind, (3) is mentally or physically incapable of testifying, (4) cannot be found, (5) is in active service of the armed forces of the United States or (6) is outside this State, the court may admit proof of the handwriting of the witness or other party and such other secondary evidence as is admissible in any court of record to establish electronic records or written contracts and may admit the will to probate as though it had been proved by the testimony of the witness or other party. On motion of any interested person or on its own motion, the court may require that the deposition of any such witness or other party, who can be found, is mentally and physically capable of testifying and is not in the active service of the armed forces of the United States outside of the continental United States, be taken as the best evidence thereof.
     (b) As used in this Section, “continental United States” means the States of the United States and the District of Columbia.