There are a number of issues being obscured in the current debate about Brain Death is 1) The position of Rav Moshe Feinstein is a matter of serious debate and disagreement. Furthermore Rav Herschel Schacter takes a much more conservative position than Rav Moshe Tendler Rav Dovid Feinstein did not have firsthand knowledge of his father's viewpoint.
JLaw by Rav Yitzchok Breitowitz
The position of R. Moshe Feinstein, whose psak could well have been definitive at least in the United States, is unfortunately a matter of some controversy. His son-in-law, Rabbi Dr. Moshe Tendler, a Rosh Yeshiva in RIETS and Professor of Biology, Yeshiva College, has vigorously argued the concept of decapitation in Mishnah Oholot.15 His position finds strong support in Iggrot Moshe, Yoreh Deah III no. 132 which seems to validate nuclide scanning as a valid determinant of death. This is also the understanding of the Israeli Chief Rabbinate,
R. David Feinstein (who admits, however, to having no inside information on the topic), and R. Shabtai Rappaport, the editor of R. Moshe responsa.16
Others, however, have interpreted his teshuvot very differently, pointing out that R. Moshe reiterated twice (indeed, in one instance two years after the "nuclide scanning" reference) that removal of an organ for a transplantation was murder of the donor.17 (R. Tendler's response: Both of those teshuvot refer to comatose patients in a persistent vegetative state who are capable of spontaneous respiration and are very much alive and not to those who are respiratordependent.) They also cite R. Moshe's express opposition to proposed "brain death" legislation in New York unless it contained a "religious exemption."18 [...]
1.
As noted, Rabbi Dr. Moshe Tendler has been the most vigorous advocate for the halachic acceptability of brain death criteria. In his capacity as chairman of the RCA's Biomedical Ethics Committee, Rabbi Tendler spearheaded the preparation of a health-care proxy form that, among other innovations, would authorize the removal of vital organs from a respirator dependent, brain death patient for transplantation purposes. Although the form was approved by the RCA's central administration, its provisions on brain death were opposed by a majority of the RCA's own Vaad Halacha (Rabbis Rivkin, Schachter, Wagner and Willig).20 [...]
5.
Rabbi Hershel Schachter, Rosh Yeshiva and Rosh Kollel of RIETS, has taken a more cautious view. Conceding that the concept of "brain death" may find support in the decisions of R. Moshe, he concludes that such a patient should be in the category of safeik chai, safeik met (doubtful life). While removal of organs would be prohibited as possible murder, one would also have to be stringent in treating the patients as met, e.g., a Cohen would not be allowed to enter the patient's room.24