"Are you saying that every person who is on the verge of death [I'm not talking about Terri] would have to undergo a court process to decide about whether their treatement should be ended?"
No, I phrased my reply badly. The obvious course of action is that all close family members confer together, preferably with information and opinions from more than one doctor. In the vast majority of families, agreement will easily be reached. Only if they cannot reach agreement would litigation occur, and if that litigation does occur, it should be decided by a jury trial.
Thinking of the issue on a personal basis, if I was ever confronted with such a decision for my husband, I would definitely consult with his sisters (my husband has no children.) Conversely, I would want him to include my children in such discussions about me. This would tends to bind the family together and avoid later acrimony or guilt feelings, as well as be likely to produce a better decision. One person can be too close to the problem and feel overwhelmed, or be too influenced by a doctor, or whatever.