Ohio Rev. Code § 2107.16: Will proved in certain cases.

(A) When offered for probate, a will may be admitted to probate and allowed upon such proof as would be satisfactory, and in like manner as if an absent or incompetent witness were dead:

(1) If it appears to the probate court that a witness to such will has gone to parts unknown;

(2) If the witness was competent at the time of attesting its execution and afterward became incompetent;

(3) If testimony of a witness cannot be obtained within a reasonable time.

(B) When offered for probate, a will shall be admitted to probate and allowed when there has been a prior judgment by a court declaring that the will is valid pursuant to division (A)(1) of section 5817.10 of the Revised Code, if the will has not been revoked.