Shulchan Arukh, Yoreh De'ah 397

<b>דיני עדות לנהוג אבילות על פיהם. ובו ב' סעיפים:</b><br>מתאבלין על פי עד אחד ועד מפי עד ועובד כוכבים מסיח לפי תומו:

One observes mourning rites on the testimony of a single witness or [on the testimony of] a witness testifying to what he has heard from an [eye-] witness or if a Gentile makes an incidental statement [regarding] one's death. citing T.H. , for the general principle is that any type of evidence on which we grant a woman permission to remarry, mourning rites are also observed (E.H. § 17, 3; Asheri M.K. III). Pes. 4a; M.K. 20b; San. 5a on the question of mourning rites observed on the evidence of a single witness. Furthermore, the principle is that in ‘any matter which eventually will be exposed people do not lie’ (v. R.H. 22b; Yeb. 93b). Although we compare mourning to the laws of evidence on which a woman is permitted to remarry, we may ask the following: In the case of a woman there is an additional reason (excluding the reason of evidence) for granting her permission to remarry, viz., ‘A woman is careful to make inquiries prior to remarriage’ ( דיקא ומנסבא ) (Yeb. 116b), which is not so in the case of mourning. How can we therefore, compare the two cases? There are, therefore, some authorities who hold that the permission granted the woman is based mainly on the evidence of the single witness. It may, however, be possible that in the case of the woman we adopt a stringent view and require both the principle of evidence plus the fact that she also makes her own inquiries, whereas in the case of mourning a lenient view is adopted and the principle of evidence alone suffices — A.H. (Evidence offered in writing is also accepted in the case of permitting a woman to remarry. E.H. ibid ). One who received a letter informing him that his near-of-kin died, and in the letter it is not stated whether it is still within or after the thirty days of mourning, the law is that if the sender is not a learned person, we presume that the deceased person was alive until the time that the letter was written and dispatched (for an exposition of this type of presumption v. A.H. a.l.). Hence, the receiver of the letter must observe mourning rites. But if the sender was a learned person, we presume that the thirty day period is over, for were it possible for the letter to reach the mourner within the thirty days of mourning, the sender would not have stated the death report without defining the matter — ShaK. But if the deceased person was his father or mother, since the adopted custom is to inform the mourner about the death of a parent forthwith, in any case, the mourner is required to observe mourning rites — Birke Yos. If it happened that in a doubtful case it was ruled for one not to observe mourning, and subsequetly it became known to the individual that originally when the doubt was entertained regarding the death of his near-of-kin, the latter had really died, and it was still at the time the doubt was entertained within the thirty days, the law is that the mourner does not have to observe mourning rites (thus corrected text of ShaK in Nek. Hak. ) supra § 396 beg. (the reason being that now since it is already after the thirty days, mourning does not obtain) — ShaK. One who receives a death report via telegram should observe mourning rites — Sh.M.B. If a Gentile offers formal testimony (not incidentally), it is not accepted — Mord.

שנים אומרים מת ושנים אומרים לא מת אינו מתאבל:

[If] two [witnesses] say, 'He died,' and two [other witnesses say, 'He did not die,' the [near-of-kin] does not observe mourning rites. § 399,