BOB ABERNETHY, anchor: A conversation now about the Terri Schiavo case, which has drawn national attention to the moral arguments about whether a person in a persistent vegetative state should be allowed to die. We want to go through the questions families ask, and should ask, with John Harvey, a medical doctor and a Catholic theologian who chairs the bioethics committee at Georgetown University Hospital in Washington.

Dr. Harvey, welcome.

Dr. JOHN HARVEY (Chair, Bioethics Committee, Georgetown University): Thank you.

ABERNETHY: How many people around the country, roughly, are in a vegetative state?

Dr. HARVEY: About 19,000.

ABERNETHY: And exactly what is a persistent vegetative state?

Dr. HARVEY: It's a permanent coma that lasts and lasts and lasts. It's caused by two things. The upper part of the brain can either be dead because of lack of oxygen due to the fact that the patient has suffered some sort of accident and the heart has stopped beating, or the individual can be poisoned or be traumatized, and the cells of the upper part of the brain are not dead but are discombobulated and don't function right.

ABERNETHY: Can you, as a physician -- can you know for sure that there's no possibility of recovery?

Dr. HARVEY: You can after you've observed the patient over a period of time, and that's why I always, in dealing with this, treat such a patient for a year. And then I can look and see whether the brain, the upper part of the brain, has disappeared -- dead, gone, nothing there and the cells can never grow back -- or the brain is still there, and the cells are still there but they're not functioning correctly.

ABERNETHY: Okay. You're convinced it's a persistent vegetative state. There's no durable power of attorney, no message from the patient.

Dr. HARVEY: That's a problem for patients.

ABERNETHY: A year has passed. There's been no change. Then what do you tell a family?

Dr. HARVEY: I will bring it up with the family, the fact that I have come to the conclusion with the proof that the brain is dead -- not just discombobulated, but dead. I would bring up the fact that it is time to think about whether we want to continue to treat this patient, because it's futile, and it is not really in the best interest of everybody to continue the treatment.

ABERNETHY: Now the pope said, just a year ago, that in that situation, when somebody is being fed food and water, that it would be akin to euthanasia, to killing them ...

Dr. HARVEY: Right.

ABERNETHY: ... to remove the tube.