Oregon Revised Statutes Probate Law § 113.055

(1) Upon an ex parte hearing of a petition for the probate of a will, an affidavit of an attesting witness may be used instead of the personal presence of the witness in court. The witness may give evidence of the execution of the will by attaching the affidavit to the will or to a photographic or other facsimile copy of the will, and may identify the signature of the testator and witnesses to the will by use of the will or the copy. The affidavit shall be received in evidence by the court and have the same weight as to matters contained in the affidavit as if the testimony were given by the witness in open court. The affidavit of the attesting witness may be made at the time of execution of the will or at any time thereafter.

(2) However, upon motion of any person interested in the estate filed within 30 days after the order admitting the will to probate is made, the court may require that the witness making the affidavit be brought before the court. If the witness is outside the reach of a subpoena, the court may order that the deposition of the witness be taken.

(3) If the evidence of none of the attesting witnesses is available, the court may allow proof of the will by testimony or other evidence that the signature of the testator or at least one of the witnesses is genuine.

(4) In the event of contest of the will or of probate thereof in solemn form, proof of any facts shall be made in the same manner as in an action tried without a jury.