A woman whose husband has either abandoned her or, being absent, has not been heard from for some time. Having no proof of her husband's death, or being without a bill of divorce from him, her status as a wife remains forever unchanged; for Jewish law does not admit the presumption of death from a prolonged absence merely, nor can a wife obtain a divorce from an absent husband.
In order to mitigate the hardship arising from such cases the rabbinical law relaxed the strict rules regarding evidence—which, to establish a fact legally, required the testimony of two competent witnesses—and accepted testimony that in other cases would not have been deemed competent. If the absent husband sent a bill of divorce to his wife, the messenger was permitted to testify that it was written and signed in his presence; and this testimony was deemed equivalent to that of two witnesses (Giṭ. 2b). Another concession was made in permitting the witnesses to attest the bill of divorce, although they could neither read nor write. The bill was read to them, and a tracing was made for their signature (Giṭ. 9b; Maimonides, "Hilkot Gerushin," i. 23).
In case the husband died while absent from his wife, the testimony of one witness was deemed sufficient to prove death (Yeb. 122b), so that the woman might not become an 'Agunah (Yeb. 88a), it being almost impossible in most cases to obtain two witnesses to prove death in a foreign land. In this case even hearsay evidence, as well as the testimony of persons otherwise utterly incompetent, was received.Maimonides ("Hilkot Gerushin," xiii. 29) sums up the matter in these words:
"Let it not seem hard to thee that the sages have permitted remarriage of the wife upon the testimony of a woman, or a slave [male or female], or an idolater [speaking without motive], or upon hearsay or documentary evidence, and without cross-examination; for the Torah insists upon the testimony of two witnesses and upon the other rules of evidence only when the matter can not be otherwise determined—as, for instance, to prove murder, or to prove a loan—but where the matter can be otherwise determined and the testimony of a witness can be refuted, as in the case where he testifies that some one is dead, it is not to be presumed that he will bear false witness. Hence, the rule is relaxed so that Jewish women shall not be 'Agunot."
For 'Agunah in history see