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Brain Death: What Catholics Should Know

By Dr. Doyen Nguyen and Dr. Joseph M. Eble

Brain death (BD), the declaration of death by neurological criteria, is an established medicolegal practice in the USA and many countries worldwide. In 1968, the Harvard Medical School Ad Hoc Committee introduced BD by defining (in the opening paragraph of its report) “irreversible coma as a new criterion for death.” BD has been a controversial issue ever since. That brain-dead donors are the primary source of organ transplants has further intensified the controversy, as evidenced by the increasing number of lawsuits challenging the legitimacy of BD. A well-known example is the McMath case.

The BD controversy is of great importance for two main reasons. First, it seems that the Church, through Pope John Paul II, has accepted BD as a valid criterion for the determination of death. Second, there is an ongoing push for changing the existing law, the Uniform Determination of Death Act (UDDA), so that it will preclude families from challenging the validity of BD. We will focus on those aspects of BD most relevant to Catholics, basing our discussion on factual evidence and the principles of Catholic anthropology.

Though people may have heard about BD, many have no clear picture thereof, thinking that BD is the same thing as death (the irreversible stoppage of all vital functions as determined by traditional cardiopulmonary criteria). The most direct approach to understand BD is to compare it with death itself. Death is both: (i) a metaphysical event — the separation of the soul from the body — which, as John Paul II indicates, “no scientific technique or empirical method can identify directly” — and, (ii) a biological phenomenon, the natural process of the somatic/bodily disintegration of the corpse. This process, which takes place immediately after the metaphysical event of death has occurred, manifests the unstoppable increasing entropy which no technological intervention can reverse. Because death is a biological phenomenon:

(i) it is species-nonspecific and applies equally to other warm-blooded mammals, such that when we say “our cousin died,” we mean the same thing as when we say “our pet dog died.”

(ii) there is a constellation of recognizable signs indicating that the once-living warm-blooded being has died. In addition to the complete cessation of all vital bodily functions beyond the possibility of resuscitation, one of the earliest identifiable signs of bodily disintegration is a rapid drop in temperature of the corpse to the level of the ambient temperature. The rapid draining of the blood from surface capillaries into the deep veins leaves the skin gray and lifeless. Other signs of death, namely livor mortis and rigor mortis, set in within a few hours.

In defining irreversible coma as a new criterion for death, the 1968 Harvard report advanced the following BD diagnostic criteria: (i) “complete unresponsiveness” even to the most painful stimuli; (ii) no spontaneous breathing as documented by the apnea test, (iii) “no spontaneous muscular movements;” (iv) no reflexes, i.e., brainstem reflexes are absent, plus “as a rule the stretch tendon reflexes cannot be elicited;” and (v) a flat encephalogram (EEG). Note that in BD, death is declared solely on the basis of the absence of those functions of the brain that can be tested clinically, and not on the basis of the stoppage of all vital functions.

In 1981, the President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research endorsed BD by promulgating the UDDA. The UDDA makes BD legal death on a par with traditional cardiopulmonary death and defines BD as “the irreversible cessation of all functions of the entire brain, including the brain stem.”

Over the course of years, the original diagnostic criteria of BD became modified such that according to the current guidelines (effective since 1995 and updated in 2010) published by the American Academy of Neurology (AAN):

(i) a bedside neurologic examination alone is sufficient for determining BD; EEG and cerebral blood flow studies are not required;

(ii) the presence of normal blood pressure and absence of diabetes insipidus, both indicative of persistent secretion of anti-diuretic hormone (ADH) by the hypothalamic-pituitary axis of the brain is compatible with BD;

(iii) spontaneous movements and various stretch reflexes of the limbs, as well as lacrimation, sweating, blushing, tachycardia, and sudden increases in blood pressure, do not invalidate a diagnosis of BD. For BD proponents, all these signs are irrelevant because they originate from the spinal cord.

Conrado Estol, a neuroscientist and participating member of the 2006 Working Group The Signs of Death, sponsored by the Pontifical Academy of Sciences (PAS), affirms that spontaneous movements and reflexes “are present in approximately 80% of patients up to 200 hours from BD diagnosis. . . . Movements [are] observed at the surgical table during organ harvesting. . . . In this context, death is not necessarily a synonym of immobility and movements can be seen in certain patients with [a] recent diagnosis of brain death.”

At this point, readers can see the difference between death and BD and raise concerns that a body that sweats, flushes, and moves is not in fact dead. Indeed, it is not uncommon that brain-dead donors receive anesthesia and paralytic drugs to prevent the occurrence of movements during the organ-removal surgery. If we compare side-by-side: (i) the brain-dead body of a soon-to-be organ donor, (ii) a living patient, and (iii) the dead body of a patient whose death was determined by traditional cardiopulmonary criteria, it is self-evident that, except for being deeply comatose, the brain-dead patient shares all the features of the living, including a beating heart, warm skin, and functioning vital organs, e.g., liver and kidneys, among others.

Moreover, there have been many reports of patients who were declared dead because they fulfilled the diagnostic criteria of BD, but who continued to live for long periods of time. Of these, the two most publicized cases are TK and Jahi McMath. TK (reported in Alan Shewmon’s series of patients with “chronic BD”) was diagnosed brain dead at age four and a half as a result of fulminant Haemophilus influenzae meningitis; he continued to survive for another 20 1/2 years. McMath was declared brain dead at age 13 by two neurologists and one intensivist, but lived until age 17. Both underwent proportionate physical growth. McMath also underwent pubertal changes, including menstruation. There were no pubertal changes in TK, as the meningitis infection had completely destroyed his brain such that, at autopsy, what was found intracranially was not a brain, but a calcified spherical mass about four inches in diameter with no identifiable neural structures either grossly or microscopically.

In sum, the biological phenomenon of somatic disintegration, which invariably follows the metaphysical event of death (the separation of the soul from the body), has been consistently absent in BD prior to patients undergoing organ harvesting or being removed from life support. It has been repeatedly argued that brain-dead patients are truly dead, and that they only seem to be alive because death is masked by medical intervention, especially the ventilator. To claim, however,  that an artificial device can camouflage bodily disintegration contradicts the principle of proportionate causes and effects, according to which a cause cannot produce that which it does not have in itself. The ventilator can only blow air in and out of the lungs. It cannot trigger the exchange of oxygen and carbon dioxide in the lungs, let alone a myriad of integrative functions throughout the body such as circulation, kidney function, immune function, and homeostasis of numerous types. Indeed, if the ventilator could mask death, then connecting it to the cold and gray corpse of a person just declared dead according to traditional cardiopulmonary criteria should make that dead body appear warm and pink, and capable of a whole host of vegetative functions. As intuited by common sense, this would not occur.

John Paul II’s Address to the 18th International Congress of the Transplantation Society in 2000 was the only time when the Magisterium spoke explicitly on the BD issue. The first question to consider is: to which category in the hierarchy of the ordinary teaching of the Magisterium does this Address belong? As stated in Donum Veritatis, the ordinary teaching of the Magisterium includes several gradations, from the highest end (e.g., encyclicals) “when the Magisterium proposes ‘in a definitive way’ truths concerning faith and morals,” to the lower end of “interventions in the prudential order, [in which] some Magisterial documents might not be free from all deficiencies” because of insufficient consideration of the complexity of an issue. Thus, in order “to assess accurately the authoritativeness of the interventions” of the Magisterium, one must pay attention to “the nature of the documents, the insistence with which a teaching is repeated, and the very way in which it is expressed.” In this regard, John Paul II’s 2000 Address belongs to the category of interventions of the prudential order. Notably, his statement on BD (article 5 of the Address) occurred only once in the whole of the teaching of the Magisterium. There is no mention of it in John Paul II’s message to the participants of the 2005 conference, The Signs of Death, (sponsored by the PAS) or in Benedict XVI’s 2008 address, A Gift for Life: Considerations on Organ Donation.

For discussion purposes, the key points of John Paul II’s Address are reproduced here:

(i) article 4: Vital organs which occur singly in the body can be removed only after death, that is from the body of someone who is certainly dead. . . . The death of the person is a single event, consisting in the total disintegration of that unitary and integrated whole that is the personal self. It results from the separation of the life-principle (or soul) from the corporal reality of the person. . . . [It] is an event which no scientific technique or empirical method can identify directly. . . . Once death occurs, certain biological signs inevitably follow . . . [indicative] that a person has indeed died.

(ii) article 5: For some time certain scientific approaches to ascertaining death have shifted the emphasis from the traditional cardio-respiratory signs to the so-called “neurological” criterion. Specifically, this consists in establishing, according to clearly determined parameters commonly held by the international scientific community, the complete and irreversible cessation of all brain activity. . . . It can be said that the criterion adopted in more recent times for ascertaining the fact of death, namely the complete and irreversible cessation of all brain activity, if rigorously applied, does not seem to conflict with the essential elements of a sound anthropology.

Many Catholic scholars have focused solely on article 5, especially, the brief and synthetic statement, “the complete and irreversible cessation of all brain activity, if rigorously applied, does not seem to conflict with the essential elements of a sound anthropology,” interpreting it as the Magisterium’s definitive approval of the neurological criterion for the determination of death. However, article 5 must be read in the context of the whole Address. In article 3, the pope alludes to human dignity, indicating that the body cannot treated as a commodity (“a mere complex of tissues, organs and functions”). In article 4, because the removal of unpaired vital organs (namely, the heart) causes death, the pope stresses the need to ensure that the person is truly dead (as evidenced by the biological signs of somatic disintegration) before proceeding to organ removal.

A critical examination of John Paul II’s statement on BD reveals that the alleged definitive approval is actually a conditional approval. This is indicated by: (i) the use of the conjunction “if,” in addition to the verb “seem” which conveys a certain degree of caution, and (ii) the three presuppositions or conditions embedded in the statement, all of which must be true or fulfilled for the conclusion (i.e., the approval of BD) to follow. First, the pope presupposes that the BD standard has been established by “clearly determined parameters commonly held by the international scientific community” — the term “parameters” refers to the diagnostic tests used for establishing BD. Those parameters would be clearly determined only if they had undergone rigorous scientific validation. However, such validation has never taken place, neither before nor after the introduction of BD into clinical practice. The parameters are not commonly held either: there exists no consensus regarding the diagnostic tests, but rather a confusion of practices with significant variability in all areas, especially regarding the apnea test, the cornerstone test for establishing BD. The writings of pro-BD scholars acknowledge this lack of consensus — for example, “Brain Death Worldwide: Accepted Fact but No Global Consensus in Diagnostic Criteria” (Wijdicks, Neurology, 2002); “Variability of Brain Death Determination Guidelines in Leading US Neurologic Institutions” (Greer et al., Neurology, 2008); and, more recently, “Worldwide Variance in Brain Death/Death by Neurologic Criteria” (supplement 1 to Greer et al., JAMA, 2020).

Second, John Paul II’s approval of BD rests on the condition that the neurological criterion is rigorously applied. However, without validation and consensus of its diagnostic parameters, one cannot proceed to rigorous application. Moreover, the standard battery of parameters (as per the AAN guidelines) is inadequate for determining the irreversible loss of all brain functions because it consists of bedside clinical tests which target only brainstem function. Thus, it is not uncommon that patients who met the bedside parameters for BD demonstrated the presence of ADH production and/or brain electrical activity on EEG testing.

Built on the condition of rigorous application is the pope’s third and most important presupposition, namely that BD “does not seem to conflict with the essential elements of sound anthropology.” The anthropology in question is the Christian anthropology founded on the Aristotelian-Thomistic doctrine of hylomorphism (the substance view of the human person) according to which man is the substantial union of matter (body) and form (soul). As stated in Summa Theologiae I, q. 76, a. 1:

“. . . the first principle by which the body lives is the soul. And as life appears through various operations in different degrees of living things, that whereby we primarily perform each of all these vital actions is the soul. For the soul is the primary principle of our nourishment, sensation, and local movement; and likewise of our understanding.”

These diverse activities of life manifest the three fundamental capacities (powers) of the human soul — vegetative, sensitive (sensory-motor), and rational — which relate to one another in a strict ontological hierarchy in which the “lower” power is the precondition for the higher power. Consequently, if there are no detectable manifestations of the highest (rational) power, the presence of the soul can still be confirmed by manifestations of its lowest yet most foundational power – the vegetative power, expressed in and through numerous integrative vegetative functions working together to keep the body integrated.

That the soul is the first principle by which the body lives means that the soul makes the body to be what it is and keeps it integrated. The soul-body substantial union means that the soul is “necessarily in the whole body, and in each part thereof”; consequently, “on the withdrawal of the soul, no part of the body retains its proper action” (ST I, q. 76. a. 8). John Paul II reiterates this very point, stating: “death . . . is a single event, consisting in the disintegration of that unitary and integrated whole that is the personal self.” However, instead of undergoing disintegration, brain-dead patients demonstrate a whole host of integrative vegetative functions including cardiovascular function, maintenance of body temperature, absorption of nutrients, and excretion of wastes, among others. Are these not the manifestations of the vegetative power of the human soul? Many brain-dead patients also demonstrate spontaneous movements and reflexes of the limbs. Are these not the manifestations of the sensory-motor power of the human soul? The reality of BD falsifies the claim that the neurological criterion is compatible with the Church’s anthropology.

Since none of the three presuppositions in the pope’s statement hold, it cannot be said that the Magisterium has given BD its stamp of approval. It appears that, at the time of his Address, the pope lacked certain key information about BD, especially the following: (i) the AAN guidelines (known since 1995), according to which death can be declared despite the presence of spontaneous movements, persistent ADH production, and other bodily activities; and (ii) the philosophical rationale undergirding BD (known since 1981), according to which the brain is the critical master organ-integrator of the body without which the human person is dead.

Such a rationale contradicts the Church’s anthropology, according to which the soul (and not the brain) is the principle animating the body, keeping it integrated, and without which the human person is dead. Furthermore, it also contradicts the well-known twofold axiom on “whole and parts” according to which the organic whole is greater than the sum of its parts and is ontologically prior to its parts. Consequently no part can account for itself, let alone for the organic whole. Since every human person begins life as a single-cell zygote and develops into an embryo before acquiring a brain, the relationship of the brain vis-a-vis the body (the human person) is that of a part vis-a-vis its greater whole, because the brain, just like any other organ or part, only comes into existence after the person has come into existence. In brief, the brain cannot account for the integration and life of the organic whole from which it develops.

Death touches every member of society. Yet the general public was excluded from the decision-making process leading up to the promulgation of the UDDA which ushered in BD as legal death on a par with traditional cardiopulmonary death. However, with a gradual increase in public awareness about BD and its connection to organ transplantation, there has been growing resistance against BD on the part of the patients’ families and an ensuing increase in lawsuits challenging the legal status of BD. The families’ legal claims are of three categories:

(i) The determination of BD (which follows the AAN diagnostic guidelines) does not satisfy the legal requirements in the UDDA. The UDDA defines BD as “the irreversible cessation of all functions of the entire brain”; but the AAN guidelines insist that ADH production by the brain is compatible with BD. Furthermore, studies have shown that in some patients who met the clinical criteria for BD, the EEG demonstrated persistent brain activity. Yet the AAN guidelines make EEG testing optional/unnecessary, which can only decrease the accuracy of ascertaining the irreversible cessation of all functions of the entire brain.

(ii) Consent is required before conducting BD diagnostic tests, especially the apnea test, in which the patient is temporarily removed from the ventilator: if no spontaneous respiration occurs, the patient fails the apnea test. Apnea testing is non-beneficial to patients in coma since it can cause various complications such as cardiac arrest, hypotension, and worsening brain swelling. Nevertheless, BD advocates argue that consent is not required because: (a) the brain-dead individual is dead, and no consent should be required for a procedure on a dead body, and (b) to require consent amounts to allowing families to opt out of a BD diagnosis.

(iii) Religious objection to a declaration of death on the basis of a BD diagnosis.

The main reason for families’ resistance to BD is the fact that their loved ones, though declared dead, still bear many signs of life. Nevertheless, BD advocates insist that such resistance is caused by variations in BD laws among the states (all 50 states have adopted the UDDA, however) and that the cause for such variations is the UDDA itself. Thus, in January 2020, leading members of the AAN proposed a “revised UDDA” (Lewis et al., “It’s Time to Revise the Uniform Determination of Death,” Annals of Internal Medicine). A detailed critique of this proposal can be found in “Does the Uniform Determination of Death Act Need to Be Revised?” (Nguyen, The Linacre Quarterly, 2020). The three most important points of the proposal are: (i) the UDDA definition of BD is changed in such way that it specifically matches the AAN guidelines, (ii) consent is not required for conducting BD tests, and (iii) provisions are included for the acceptance of future revisions of the AAN guidelines. In brief, the strategy used in the proposed “revised UDDA” is one in which the law regarding BD can be manipulated to become subservient to the AAN guidelines. This proposal has been submitted to official legal authorities for ongoing deliberation. If passed into law, it will effectively preclude families from objecting to either BD testing or a BD diagnosis, thereby eliminating all possible lawsuits.

This essay has presented the most relevant information regarding BD, most of which, to our knowledge, has not been made available to the general public, including Catholics. We have provided ample evidence both empirically and philosophically that BD is not the same thing as death simpliciter (death understood as the separation of the soul from the body, followed by the biological signs of somatic disintegration).

The issue of BD is of practical importance since most people have a driver’s license. At the time of obtaining that license, people can choose whether or not to become an organ donor. They are not informed, however, that by choosing “yes,” they implicitly accept that they can be declared dead on the basis of the neurological criterion.

Because of the tight connection between BD and organ transplantation, the fact that BD is not the same thing as death simpliciter is of ethical significance. However noble the purpose of organ transplantation, it cannot harm the life of a dying person in irreversible coma (which the Harvard report defines as the new criterion of death). Here, it helps to recall both the teaching in Romans 3:8 that we cannot do evil to achieve good and the teaching of Pius XII who, in 1957, affirmed that “human life continues for as long as its vital functions . . . manifest themselves spontaneously or even with the help of artificial processes.” This is why John Paul II, in his 2000 Address, admonished that “what is technically possible is not for that reason morally admissible” (article 2). Benedict XVI’s subsequently reaffirmed in 2008 that “individual organs cannot be extracted except ‘ex cadavere’ [and] the principal criteria of respect for the life of the donor must always prevail so that the extraction of organs be performed only in the case of his/her true death.” The statement which Benedict XVI made as Cardinal Ratzinger in his 1991 discourse, The Problems of Threats to Human Life, is even more explicit:

“Today we are the witnesses of a true war of the mighty against the weak, a war which looks to the elimination of the disabled . . . in all the moments of their existence. With the complicity of states, colossal means have been used against people, at the dawn of their life, or when their life has been rendered vulnerable by accident or illness, . . . [in particular,] those whom illness or accident cause to fall into an ‘irreversible’ coma will frequently be put to death to answer the demand for organ transplants or they will even be used for medical experiments (‘warm cadavers’).”

As John Paul II indicated, “the Church does not make technical decisions.” Nevertheless, she has the “duty of comparing the data offered by medical science with the Christian understanding of the unity of the person” (article 5). It would be most helpful if the United States Conference of Catholic Bishops, and ultimately the Magisterium, could issue a clarification of that Address based on a careful study of the medical aspects of BD (in particular the AAN guidelines) in light of the essential elements of the Church’s anthropology. Such a clarification would help to dispel the confusion among Catholics with respect to BD. In the meantime, it is hoped that this essay will help Catholics make a well-informed decision regarding organ donation-transplantation from brain-dead donors, and assist them to be proactive regarding the impending likelihood of the promulgation of a “revised UDDA,” one that will take away the rights to refuse BD tests and to contend a BD diagnosis.

Doyen Nguyen, OP, MD, STD, is a lay Dominican, retired academic hematopathologist, Catholic moral theologian, and bioethicist. She has authored books and articles both in medicine and in moral theology/bioethics. Among her recent publications are the 600-page monograph The New Definitions of Death for Organ Donation: A Multidisciplinary Analysis from the Perspective of Christian Ethics (Peter Lang, April 2018. ISBN 978-3-0343-3277-4) and an article on the topic of brain death, “Does the Uniform Determination of Death Act Need to Be Revised?” (The Linacre Quarterly, 87(3):317-333, 2020).

Joseph M. Eble, MD, is president of the Tulsa Guild of the Catholic Medical Association, a member of the Tulsa Chapter of Legatus, and a managing partner of Fidelis Radiology. Subjects about which he is passionate include brain death, adoption, and building bridges between persons of different ethnicity. His most recent published article on the topic of brain death is “Implications of John Kavanaugh’s Philosophy of the Human Person as Embodied Reflexive Consciousness for Conscientious Decision-making in Brain Death” (The Linacre Quarterly, 88(1):71-81, 2021). He may be reached at

This article has been reprinted from the Homiletic and Pastoral Review at and is reprinted here with permission.