21 GCA § 33117: Handwriting Generally.

The execution of an instrument may be established by proof of the handwriting of the party and of a subscribing witness, if there is one, in the following cases:

(a) When the parties and all the subscribing witnesses are dead; or,

(b) When the parties and all the subscribing witnesses are nonresidents of Guam; or,

(c) When the place of their residence is unknown to the party desiring the proof, and cannot be ascertained by the exercise of due diligence; or,

(d) When the subscribing witness conceals himself, or cannot be found by the officer by the exercise of due diligence in attempting to serve the subpoena or attachment; or,

(e) In case of the continued failure or refusal of the witness to testify, for the space of one hour, after his appearance.