In a major right-to-die case, the court ruled 6-to-0 this morning that the wife of a Stockton man severely injured in a car accident could not withdraw his feeding tube because he had left no formal instructions of his wishes.

Robert Wendland, 49, died last month of pneumonia after a six-year battle in which his wife said he should be allowed to die and his mother fought to keep him alive.

The case drew wide attention because Wendland was not in a coma or near death. Instead, he lingered in a twilight state that some doctors described as "minimally conscious."

He was paralyzed on his right side and could not speak, walk or control his bowel functions.

His wife and three children said he did not recognize them. But his mother said he kissed her hand and could play catch with a ball.

His wife and brother said Robert Wendland told them before the accident that he did not want to be in a vegetative state.

But the justices said today that those statements were not enough.

A conservator must show "by clear and convincing evidence, either that the conservatee wished to refuse life-sustaining treatment or that to withhold such treatment would have been in his best interests," Justice Kathryn Mickle Werdegar wrote in the 47-page decision.

The court said its ruling would not affect most decisions made by conservators of loved ones no longer competent to make their own choices.

"Only the decision to withdraw life-sustaining treatment, because of its effect on a conscious conservatee's fundamental rights, justifies imposing that high standard of proof," Werdegar wrote.

"The decision to treat is reversible. The decision to withdraw treatment is not."

The court overturned a state appeals court decision that rejected the "clear and convincing" standard, saying the law only requires the wife, Rose Wendland, to act in good faith as her husband's conservator.

San Francisco attorney James Braden, who was appointed by the court to represent Robert Wendland, said that the decision "eliminates the practical usefulness of a conservator's decision to end life-sustaining treatment."

"It's unfortunate that the court has chosen a course so far outside the mainstream of bioethical thinking," said Oakland lawyer Jon Eisenberg, who filed a friend-of-the-court brief on behalf of six health care associations and 43 individual bioethicists.

Robert Wendland was severely injured in September 1993, when his truck rolled over in a solo accident. He had been drinking before the accident.

He was in a coma for several months and eventually regained consciousness.

With therapy he was able to throw and catch a ball and operate an electric wheelchair with assistance. But he remained severely disabled both mentally and physically.

Two years later, Rose Wendland asked that her husband's feeding tube, which had come out several times, not be reinserted. The hospital's ethics committee agreed to her request. But Wendland's mother received an anonymous call from a hospital telling her of the plan.

Florence Wendland obtained a restraining order preventing her son's wife from taking any action.

During the trial, Rose Wendland said that her husband had told her before he accident that he would not want to be kept alive in a vegetative state.

Just before the accident, Rose Wendland decided to turn off the life- sustaining respirator for her father, who was near death from gangrene. "I would never want to live like that and I wouldn't want my children to see me like that," she recalls Robert Wendland telling her.

But the trial judge held Rose Wendland to a high standard, saying that she failed to show with clear and convincing evidence that Robert would want his life-sustaining treatment to be withdrawn. He noted that Robert Wendland was not in a persistent vegetative state nor suffering from a terminal illness.

A state appeals court reversed that decision, saying that the trial judge set too a high standard.

Yesterday's decision deals with an unsettled area of the law. Courts have recognized that a competent person has a fundamental right to refuse life- sustaining medical treatment.