It is important for lawyers and others considering this issue to realise how frequently such decisions are now made informally as part of good practice, outside the controversy with respect to vegetative patients.

If human life is "inviolable," then why should it matter whether a hopelessly vegetative patient - someone like Terri Schiavo - left instructions not to be fed?

Schiff began to gather some clues to this question when he switched from studying vegetative patients to people in minimally conscious states.

They arranged for the patients to have PET scans to measure their brain metabolism, as Schiff had done in his earlier study on vegetative patients.

However, some bioethicists believe that the case, if confirmed, may provide stronger arguments for withdrawing or withholding from vegetative patients.

State law varies and is often murky on how much flexibility doctors have in treating ailments of demented or vegetative patients whose desires are unknown.

Medical experts say the tearing witnessed by the nurses is also a common reflex response of persistent vegetative patients.

Very few do after that, and a 1994 review of more than 700 vegetative patients found that none had done so after two years.

A 1994 review of more than 700 vegetative patients found that none had done so after two years.

These results show that parts of the cortex are indeed still functioning in 'vegetative' patients (Matsuda et al., 2003).