When it appears that a will cannot be proved as otherwise provided by law because at the time the will is offered for probate one or more of the subscribing witnesses to the will is dead or mentally or physically incapable of testifying or otherwise inaccessible, the court may admit the will to probate in common or solemn form upon the testimony in person or by affidavit or by deposition of at least two credible disinterested witnesses that the signature to the will is that of the individual whose will it purports to be or upon other sufficient proof of such signature. This Code section shall not preclude the court, in its discretion, from requiring, in addition, the testimony in person or by deposition of any available subscribing witness or proof of such other pertinent facts and circumstances as the court may deem necessary to admit the will to probate.