Separating Conjoined Twins: Part II-Rav Moshe’s Position on Rodeif & Relative Degrees of Pursuit by Rabbi Chaim Jachter

Editors’ note: To read the first part of this series, please visit the Halachah Files section on the Kol Torah website,

We began last week to discuss the landmark case presented to Rav Moshe Feinstein in 1977 as to whether one may sacrifice one conjoined twin to save the other.  Rav Moshe permitted the surgery but did not compose a responsum to explain his reasoning.  Various explantions are offered to explain his ruling and we continue with the attempt to explain this decision, based on the Halachot of Rodeif


Another circumstance in which Halachah permits (and even requires) killing one individual to save another, is a situation of Rodeif (Rambam Hilchot Rotzeiach Ushmirat  HaNefesh 1:9).  One must kill an individual who is attempting to kill someone.  Perhaps one of the twins can be construed as a Rodeif since she is threatening the life of her twin.  The Rambam (ibid.) seems to believe that even a baby potentially may be classified as a Rodeif even though it has no malicious intent. 

Nonetheless, the status of each twin as a Rodeif neutralizes the license to kill one to save the other.  Rav Akiva Eiger (Ketubot 33b) states that Halachah forbids lethal intervention in a situation of mutual pursuers.  For example, if one were witness to the duel between Aaron Burr and Alexander Hamilton one would be forbidden to kill one of them to save the life of the other.  Similarly, since each of the two twins pursues the other’s life, the Halachah does not grant permission to kill one to save the other.  This case is similar to the aforementioned Mishnah in Ohalot which forbids killing the baby in order to save the mother after the baby’s head has emerged from the birth canal.

Two Possible Analogies

The Philadelphia Inquirer cited two analogies supposedly used by Rav Feinstein in reaching his decision to permit the surgery. The first is a case where two men jump from a burning airplane. The second man's parachute does not open and as he falls past the first man, he grabs his legs. If the first man's parachute cannot support both men, can he kick off the second man in order to save his own life? The answer is yes, because the second man is considered a pursuer (Rodeif) whose actions will result in killing the first man. According to Halacha, a pursuer can be killed in order to save the life of the pursued.

Rav J. David Bleich writes that the concept of the pursuer here is not entirely analogous to the case of the conjoined twins. In the case of the parachutes, he writes, it is clear who is the pursuer and who is the pursued, but in the case of the twins, then-current medical experience showed that the twins were mutual pursuers, each one threatening the other. The law of the pursuer does not apply when two people pursue each other, and third-party intervention in such cases is not Halachically justified. Unless it could be proven that the heart belonged exclusively to one of the twins and the other was clearly a parasite (and therefore a pursuer), the dilemma could not be easily resolved.  Rav Bleich insists that there is no way to prove that the heart belonged to either of the twins.  Rather, he strongly argues that the heart was jointly “owned” by both twins.

Saving a Mother by Killing a Fetus

However, there is a situation in which Halachah permits killing one of two mutual pursuers to save the other.  The aforementioned Mishnah in Ohalot states “A woman whose life is endangered in hard labor is permitted to have the pregnancy terminated”.  Rambam (ad. loc.) explains that the fetus is considered to be like a Rodeif to the life of the mother.  This interpretation is astounding (as noted by Rabi Akiva Eiger to Ohalot 7:6), since if the fetus is construed as a Rodeif, why is it forbidden to kill the baby to save the mother after it has emerged from her body?  For a list of sources of the solutions offered to resolve this difficulty, see Rav Bleich’s Contemporary Halachic Problems 1:347-349.

Rav Moshe Feinstein (Teshuvot Igrot Moshe Y.D. 2:60) resolves the problem as follows.  Rashi (Sanhedrin 72b s.v. Yatza Rosho) asserts that a fetus is considered only potential life until it emerges from its mother’s body.  This manifests itself in Halachah’s exempting the murderer of a fetus from death.  Thus, explains Rav Feinstein, the mother and the fetus are mutual pursuers but “unequal pursuers”.  The mother is pursuing only a potential life yet the fetus is pursuing one who is fully alive.  Accordingly, the fetus is a qualitatively greater rodeif  than the mother.  Therefore, Halachah sanctions destroying the fetus to save the life of the mother.

Rav Moshe in light of the Yerushalmi

As recorded in the Talmud Yerushalmi, Terumot 8:10, if heathens designate an individual for execution and threaten to annihilate the entire company if that person is not delivered to them, Rabi Yochanan permits the threatened individuals to turn over the designated victim. Rashi (Sanhedrin 72b s.v. Yatza Rosho) explains that, based upon the Sheva ben Bichri incident, Rav Yochanan reasons that such an act is permissible because the designated individual is destined to perish in any event, either alone if delivered to those demanding his life or together with the entire company if that demand is not satisfied.Rav Feinstein, Teshuvot Igerot Mosheh, Yoreh Deah, II, no. 60, Anaf 2 and Anaf 3, raises a serious question: It is indeed the case that the designated victim will inevitably die. However, if he is delivered to those who intend to kill him, he will be killed immediately, but, if he is not delivered to them, he will survive for at least a brief period of time until the evil individuals carry out the execution of the entire company. Certainly in the paradigm involving the handing over of Sheva ben Bichri to Yoav the death of Sheva ben Bichri would have been delayed at least until the siege of the city had accomplished its objective. Since hastening the death of even a dying patient (Goseis) is a capital crime, asks Rav Moshe, how could Rabi Yochanan sanction an act whose effect was to hasten the death of a designated victim?

Rav Moshe explains that the general rule is that if each of two individuals threatens the life of the other the law of Rodeif does not apply. In cases of mutual pursuers bystanders may not intervene because there is no reason to prefer one over the other in light of Halacha’s presumption that both lives are equally "sweet". The Gemara (Sanhedrin 74a) establishes the rule that a person may not take the life of another even in order to save his own life on the basis of the  principle "How do you know that your life is sweeter than the life of your fellow?" (Mai Chazit DaDameich Sumak Tefei).  However, argues Rav Moshe, when one of the two individuals is engaged in an act of pursuit that is qualitatively greater than that engaged in by the second pursuer, the objection in the form of "How do you know that the life of one is sweeter than the life of the other?" is removed.

In the case discussed by the Talmud Yerushami, the designated victim is entirely innocent and is not at all engaged in an overt act of aggression. Nevertheless, the very existence of the designated victim poses a threat to others and hence he is judged to be a "Rodeif". The situation depicted in the Talmud Yerushalmi, then, involves two pursuers: the victim who endangers those who continue to harbor him and the others who seek to deliver the designated victim to the murderers and who thereby themselves become the victim's pursuers. However, the nature of their pursuit is quite different from the "pursuit" of the designated victim. The victim, by virtue of his continued existence and presence among the members of the group threatens the normal longevity anticipation of those surrounding him; the others, in delivering the victim, jeopardize only the brief period of time (Chayei Sha’ah) that the victim's life would have been prolonged until he is actually seized by those making the threat.

Thus, argues Rav Moshe, Rabi Yochanan reasons that, although both parties are pursuers, the victim poses a threat to the others that is qualitatively greater than their threat to him. Elimination of the designated victim rather than allowing the others to be put to death results in a net gain in the qualitative category of life preserved, normal longevity anticipation as opposed to Chayei Sha’ah (temporary elongation of life).

In support of this approach Rav Moshe cites a discussion of the Talmud Yerushalmi (Shabbat 14:14). That discussion focuses upon whether the law of Rodeif is applicable in instances in which the pursuer is a Katan (minor). In a tentative attempt to demonstrate that a Katan, by virtue of his lack of legal capacity, cannot be designated as a Rodeif, the Yerushalmi cites the statement of the Mishnah (Ohalot 7:6) "If the major portion (of the fetus) has emerged he may not be touched for one life may not be set aside on behalf of another." In effect, the Yerushalmi regards the emerging fetus as a Rodeif as indeed does Rav Chisda in a similar discussion recorded in the Talmud Bavli (Sanhedrin 72b). However, unlike the Gemara, Sanhedrin 72b, the Talmud Yerushalmi rebuts that contention with the declaration that, in the situation to which reference is made in Ohalot, "You do not know who is killing whom," i.e., mother and child are mutual pursuers. Korban HaEedah and Penei Moshe, in their commentaries ad locum, explain that comment in explaining that, since each is endangering the other, it is not possible to make a determination that the child is pursuing the mother, or vice versa, that the mother is pursuing the child. Accordingly, there are no grounds for intervention. Rav Moshe further asserts that, in light of the comments of the Talmud Yerushalmi, the distinction drawn by the Gemara, Sanhedrin 72b, that in the case of the women in very difficult labor "it is Heaven that pursues her," must be understood in an identical manner, i.e., as an assertion that since nature causes mother and child to become locked in mutual pursuit of one another, they must be regarded as mutual pursuers with the result that the law of Rodeif becomes irrelevant.

Rav Moshe further maintains that Reish Lakish, who disagrees with Rabi Yochanan in maintaining that the specified victim may not be delivered to death even though he has been marked for death by the murderers and is destined to die in any event, does not challenge the basic thesis concerning relative degrees of Rodeif. Reish Lakish, argues Rav Moshe, maintains that a person cannot be deemed to be a Rodeif simply because evildoers arbitrarily and capriciously seek his death and will cause others to perish in order to kill their intended victim as well. In effect, Reish Lakish contends that the only Rodefim are the murderers; the individual designated by them, who is entirely passive, is not a pursuer but a victim. Only when the individual identified for execution deserves the death penalty does Reish Lakish agree that he may be delivered to the heathens, i.e., only when he has committed an overt act that gave rise to the danger is he regarded as a Rodeif. Consistent with that view, Rav Moshe cites the Taz (Yoreh Deah 157:8) in insisting that the act for which the murderers seek to punish the designated victim need not necessarily constitute a capital crime according to Halacha, but that any act sufficient to disturb the murderers renders the individual a pursuer. The case of a fetus threatening its mother in very difficult labor is significantly different from the case of an individual whom the murderers demand be delivered to them. It is not simply the existence of the fetus that threatens the life of the mother, but rather the activity of the fetus as it attempts to force its way through the birth canal that constitutes the source of danger. That activity is, of course, both natural and not the chosen act of the fetus; however, as both the Talmud Yerushalmi and the Talmud Bavli, Sanhedrin 72b, conclude (in Rav Moshe’s view), the law of Rodeif applies even to an unintentional pursuer.


In next week’s issue of Kol Torah, we will present Rav Bleich’s explanation of Rav Moshe’s conjoined twin ruling in light of his approach regarding the relative degrees of pursuit found by the case of Rodeif.

Separating Conjoined Twins: Part III - Tereifah & Rav Moshe Feinstein’s Ruling by Rabbi Chaim Jachter

Separating Conjoined Twins: Part I by Rabbi Chaim Jachter