(Correction: Because of an editing error, a story on Tuesday's Nation pages about the legal aspects of allowing a severely damaged person to die when the patient's wishes are unclear incorrectly said the brain stem of car accident victim Nancy Cruzan was not functioning. Cruzan's brain stem was functioning.)
WASHINGTON -- Legal maneuvering over removing Terri Schiavo's feeding tube has highlighted a murky and little-developed area of law: how to decide whether to allow a severely brain-damaged person to die when the patient's wishes are unclear.
If Schiavo was pronounced brain dead, there would be no controversy. She would be legally dead, and the hospital would allow her to be taken off life support even if a relative objected. Had she left written instructions -- a living will laying out her desires or a health proxy, someone to make the decision -- there would also be no dispute.
Schiavo's case is unclear. She shows some signs of brain stem activity, though doctors have diagnosed her as being in a persistent vegetative state. She left no written instructions about whether she would have wanted life-sustaining medical treatment.
Her case has triggered a contentious area of the law known as the doctrine of ''substituted judgment." That term refers to others deciding whether someone else would have wanted to die, a subjective and emotional guessing game.
''It's very important when people are talking about a 'right to die' to distinguish between a situation where a person is making his own choice to be terminated at a particular point, which courts are more and more liberal about, and a 'substituted judgment' situation," said Martha Field, a Harvard Law School professor.
It is rare for any court to be involved. If the family and a hospital ethics committee agree that ending life support is what the patient would have wanted, a doctor can remove the feeding tube without asking a judge for permission. That is usually what happens.
In this case, however, Schiavo's parents strenuously objected to the decision by her husband and her doctors to allow her to die, sending the matter to a Florida judge. After the state courts ruled that the tube should be removed, Congress passed an extraordinary law giving federal courts jurisdiction to review the Schiavo case anew.
Be they family members or judges, surrogate decision-makers are to consider a patient's prior statements, personality, philosophy, ethics, and religious values in order to extrapolate what the patient would have wanted.
Alice Herb, a lawyer and medical ethicist at Sarah Lawrence College, said there is a hierarchy for whose testimony is given the most weight: first the spouse, then children over 18, parents, siblings, and finally close friends.
But there is no uniform standard for making the decision. Some states require only a ''preponderance of the evidence" that the person would have wanted to die. Other states, including Florida, require ''clear and convincing evidence."
The pioneering case involved Karen Ann Quinlan, a 21-year-old who suffered brain damage and lapsed into a persistent vegetative state in 1975 after swallowing alcohol and Valium at a New Jersey party. Her parents fought a long legal battle in state courts to remove her respirator, which was believed to be keeping her alive. Ironically, Quinlan kept breathing after it was removed, and remained in a coma until she died in 1985.
In 1980, the Massachusetts courts faced a similar issue in the case of Earle Spring, a ''senile" man being kept alive through kidney dialysis. A state probate judge ruled that Spring would choose not to stay alive, and gave his doctor, wife, and son the power to decide whether to stop the dialysis. His son appealed the case to the Supreme Judicial Court, which ruled that the judge should have directly ordered the treatment stopped instead of delegating the decision.
The US Supreme Court, which has twice declined to intervene in the Schiavo case, has acted in a precedent-setting case: that of Nancy Cruzan, whose brain stem was not functioning because of a car accident in 1983. The National Institute of Neurological Disorders and Stroke says that vegetative patients ''have lost their thinking abilities and awareness of their surroundings."
Her family asked a Missouri judge for permission to remove her feeding tube, but the judge ruled they had not provided ''clear and convincing evidence" that Nancy would want to die.
The Cruzans asked the US Supreme Court to impose a lower standard of proof on Missouri, but the court ruled that the state could set its own standards. The Cruzans later brought new evidence before a state judge, who allowed her feeding tube to be removed in 1990.