But it is my understanding that the USSC has not ruled on euthanasia procedures per se but left that (unlike abortion) to the states. So, it is state law that now allows horrors like that in Clearwater, FL. The USSC did rule in the Cruzan case that "clear and convincing evidence" from the victim was needed to starve and dehydrate a disabled person. Of course, there is no such "evidence" in Terri's case: only what George W. Greer and George J. Felos dictate.
And you do notice that Terri's attornies never argued that point. Just like they didn't notice the error in Greer's opinion that Karen Ann Quinlan was alive until 1985 when Greer said she died in 1976.
There was little true evidence for Nancy Cruzan either. They went and dug up some coworkers from 8-10 years prior to her accident to testify that she would not want to live as she was living.