In the past half-century, death has been transformed by scientific, technological and social changes. Today, about 80% of Americans die in a health care facility. Some milestones:

1950s

Respiratory support, particularly by ventilators, gains widespread use to sustain polio patients.

1960s

1963: Kidney dialysis invented in Seattle.

1965: Medicare increases access to medical care for millions of Americans, raising new ethical questions: How much to spend? How far to go?

1966: National Academy of Sciences recommends training physicians in the new lifesaving technique of cardiopulmonary resuscitation.

1965-68: National Institutes of Health revolutionizes research and treatment ethics, calling for informed consent for tests, surgeries and procedures.

1967: The first successful heart transplant prompts Harvard anesthesiologist Henry Beecher to seek a new criteria for death to allow transplants of vital organs while the heart is still beating.

1968: Harvard Ad Hoc Committee to Examine the Definition of Death adds brain-death criteria — irreversible cessation of all functions of the entire brain — to the traditional heart-death definition.

1970s

New ventilator technology revolutionizes cardiopulmonary care in intensive-care units. People who will never breathe again without help can be sustained for years.

1976: Karen Ann Quinlan case in New Jersey Supreme Court establishes legal right for a surrogate to make decisions for an incompetent patient. Quinlan's parents successfully fought to remove their daughter, who was in a persistent vegetative state, from a ventilator.

1980s

1981: President's Commission for the Study of Ethical Problems in Medicine writes the Uniform Determination of Death Act, incorporating brain-death definition.

Mid-1980s: Development of artificial nutrition and hydration, often delivered by a feeding tube.

1990s

1990: U.S. Supreme Court establishes that adults have a right to refuse medical treatment, but states may require clear and convincing evidence if a surrogate seeks to refuse treatment for an incompetent patient. Nancy Cruzan's parents won the right in Missouri court to remove a feeding tube sustaining their daughter, who was in a persistent vegetative state.

1990: The Federal Patient Self-Determination Act requires every patient in a medical facility to be informed about his or her medical rights and ability to decline unwanted medical interventions.

1994: Oregon approves Death with Dignity Act, allowing physicians to help a terminally ill patient die by prescribing a narcotic overdose. It survived a repeal vote and takes effect Jan. 1, 1998.

1997: Two Supreme Court rulings recognize states' decisions on physician-assisted suicide.

2000s

2005: Court and legislative battles over brain-damaged Terri Schiavo, who had been sustained by a feeding tube for 15 years, ignite a national legal and religious conflict over the definition of death, the right to die and the validity of surrogate decision-making without a written directive. Traditional Catholics and Protestants, liberals of many faiths and secularists see the issues unresolved by Schiavo's death on March 31.

2005: The Justice Department legal challenge of the Oregon Death with Dignity Act will be heard by the U.S. Supreme Court today.

Sources: USA TODAY research; Tom Beauchamp, Kennedy Institute of Ethics, Georgetown University; William Colby, Center for Practical Bioethics; Timothy Quill, professor of medicine, psychiatry and medical humanities, University of Rochester Medical Center, Rochester, N.Y.