“Brain death” was introduced to the world, in 1968, by a committee at Harvard Medical School. “Responsible medical opinion,” the committee reported, “is ready to adopt new criteria for pronouncing death to have occurred in an individual sustaining irreversible coma as a result of permanent brain damage.” People on ventilators in intensive care units, their brains destroyed by trauma or disease, their hearts still going strong, may have been breathing, taking in nourishment, excreting waste, and healing from infection, but, at least in the opinion of doctors, they were dead—“heart-beating cadavers,” as bioethicists came to call them. Thirteen years later, the President’s Commission for the Study of Ethical Problems in Medicine and Biomedical and Behavioral Research endorsed this opinion, recommending that all states adopt statutes to give doctors the right to pronounce brain-dead people legally deceased. Today, in every state, if your brain, including the brain stem, has been irreversibly and completely destroyed, you are dead.

As I wrote in the magazine, in 2001, death was legally redefined, in large part, to facilitate organ donation, a practice that, because of advances in immunosuppression and surgical technique, was increasingly effective, and, therefore, frequent. People in need of organs were, in the words of Henry Beecher, the Harvard committee member credited with writing the report, “stacked up waiting for suitable donors.” As Beecher knew, patients on life support—a population that was growing, thanks to the increased efficacy of intensive-care units—were the definition of the suitable donor, because their hearts still beat well enough to perfuse the organs with oxygen, keeping them viable. But such people were, according to the laws of the time, still alive. To Beecher, this was an outrage of inefficiency. “Can society afford to discard the tissues and organs of the hopelessly unconscious patient when they could be used to restore the otherwise hopelessly ill, but still salvageable individual?” he asked. If, on the other hand, brain-dead people were legally dead, then the supply problem was solved: transplant doctors could remove a still-beating heart (and a patient’s other organs) without committing murder.

Among the challenges that advocates of the new definition of death faced was explaining to the public why this redefinition was not simply a conceptual gerrymander. Was there some reason, other than “responsible medical opinion,” to move life’s most enduring boundary? In recommending the adoption of brain-death laws, the Presidential bioethics commission provided a rationale: the brain-dead person was dead because the brain was the maestro that conducted the body’s various instruments, and, without it, the body no longer exists as an integrated whole. Indeed, the committee concluded, the reason that cardiac arrest constituted death was that, when the blood stopped flowing, the brain eventually died. Brain death had always been the true death; we just didn’t know it.

As effective as these two committees were at putting to rest the anxiety that transplant doctors were high-tech grave robbers, they could not possibly have foreseen developments like the advent of the Internet, the health-care funding crisis, the debate over medical malpractice, state-by-state tinkering with concepts of life and death, rising suspicions about the authority of public institutions, and the deteriorating sway of medical opinion. Those are among the factors that fuelled two recent cases, one in California involving a thirteen-year-old girl who suffered surgical complications, and one in Texas, involving a thirty-three-year-old pregnant woman who became comatose for unknown reasons. The furor over these tragedies indicates that the hard-won consensus about brain death is more fragile than anyone might have thought.

Each case is heartbreaking in its own way. In California, a thirteen-year-old girl, Jahi McMath, hemorrhaged after throat surgery performed at Oakland Children’s Hospital on December 9th. Blood loss deprived her brain of oxygen, and she lapsed into a coma. On December 11th, her doctor called the neurologist Robin Shanahan to determine, as the attending physician put it to the court, “whether or not Ms. McMath had sustained an irreversible cessation of all functions of the entire brain.” Shanahan detected no brain activity. On December 12th, McMath was declared dead, and a death certificate was issued.

While the families of the brain-dead usually take doctors at their word, or at least accept that their loved one’s life is over, something went wrong; both the hospital and the family lawyered up. The hospital portrayed the family as ignorant. “There is absolutely no medical possibility that Ms. McMath’s condition is reversible or that she will someday recover from death,” Shanahan told the California Superior Court. Meanwhile, experts consulted by the McMaths’ legal team—who included a “forensic-intelligence analyst,” an Ohio doctor who concluded that the teen-ager was reacting to the presence of her family and thus could not be dead, along with a lawyer known for his opposition to California’s malpractice laws—insisted that Oakland Children’s had misdiagnosed her.

“Plaintiffs are Christians with firm religious beliefs that as long as the heart is beating, Jahi is alive,” the lawyer wrote in a brief filed after the hospital refused to comply with McMath’s parents’ wish to prepare her for transfer to a rehabilitation facility, on the grounds that a tracheotomy and other procedures would amount to providing treatment to a corpse. National media interest followed, featuring, among other angles, the possibility that the hospital had declared McMath dead in order to limit its malpractice liability to the two-hundred-and-fifty-thousand-dollar limit imposed by California law in the case of a child’s death—or, conversely, that the family resisted the diagnosis in order to reap the much higher damages available for a permanent injury. On January 7th, McMath, still on a respirator, was transferred to another facility for care.

In the Texas case, the roles of the family and hospital were reversed. Shortly before Thanksgiving, thirty-three-year-old Marlise Machado Muñoz got out of bed to check on her crying child in the middle of the night. Her husband, Erick Muñoz, a paramedic, got up and discovered her on their kitchen floor, unconscious and not breathing. She had been there at least an hour, and neither his attempts nor those of emergency-room personnel could revive her. At John Peter Smith Hospital, in Fort Worth, her heart stopped beating, multiple times. The family, in accordance with her wishes, told the staff not to make further resuscitation attempts, but was informed that the hospital could not comply: she was fourteen weeks pregnant, and Texas law forbids withdrawing or withholding life support from a pregnant woman until the fetus is viable and can be delivered. Later, according to Erick Muñoz, doctors told him his wife was brain-dead, but would be kept on the machines for at least another twelve weeks.

As if the end-of-life dilemma it presented weren’t complicated enough, the Muñoz case became a beginning-of-life dilemma as well. Abortion-rights activists charged state lawmakers and hospital officials with turning Marlise Muñoz into an incubator. A spokesman for the Texas Catholic Conference expressed “sympathy for those going through this grief and tragedy. But the fact is, this is still a life. Life begins at conception.” The hospital sidestepped that question. “This is not a difficult decision for us,” a hospital spokesman told the Associated Press. “We are following the law.” Some, including a couple of the experts who helped draft the law, tried to put aside the question of fetal rights. They insisted, instead, that the law was meant to bar removing life support from a living woman carrying a child—not the body of a woman who had died while pregnant. Muñoz “is neither terminally nor irreversibly ill,” said one of the experts. “Under Texas law, this patient is legally dead.”