We have previously referred to the special leniency that allows a woman to remarry on the testimony of one witness. This was a most revolutionary innovation, one that seemingly violates a fundamental precept of the Torah: the basic requirement for two witnesses. Compounding the problem was the fact that the stakes were so high--adultery, illegitimate children, and the undermining of the holiness of marriage--and it is no wonder this law was not readily accepted.
"A woman whose husband went overseas, and one came and told her, 'Your husband has died' and she marries [another]..." (Yevamot 87b). Whereas Jewish law requires two witnesses in all matters of criminal and family law, when it comes to freeing a woman who is "chained" to her missing husband, this law is relaxed, allowing the woman to remarry based on the testimony of only one witness.