Ala. Code § 12-21-62

Whenever the subscribing witnesses to an instrument in writing are dead, insane, incompetent or are without the state or their residence is unknown or, being produced, they do not recollect the transaction, then proof of the actual signing by, or of the handwriting of, the alleged maker or subscribing witness shall be received as primary evidence of the fact of execution; and, if such evidence is not attainable, the court may admit evidence of the handwriting of the subscribing witnesses or other secondary evidence to establish such fact of execution.