Ala. Code § 12-21-61: Subscribing Witnesses - When Must Be Produced.

The subscribing witness to prove execution of private documents must be produced in all cases except the following, unless otherwise specially provided:

(1) Ancient writings which prove themselves;

(2) If from any cause the witness cannot be produced or sworn;

(3) Official bonds required by law to be approved or tested by a particular functionary;

(4) If the paper is only incidentally or collaterally material to the case;

(5) If the party executing the written instrument testifies to its execution; or

(6) If the document is self-proving or properly acknowledged.