this is not a right to die case. your first premise is incorrect. if the convict has rights under the constitution so does Terri. Terri is not less of a person because she needs a wheelchair. It appears you think TErri is less of a person. YOU SHOULD BE A FLORIDA JUDGE. THEY HAVE NO QUALIFICATIONS EITHER.
Why cut off your own paycheck when your "client" can never disagree with you ?
I'm not fond of lawyers. Having said that, a guardian ad litem could make sure any documents stating the patient's wishes were legitimate and made in sound mind. The GAL would look for signs that family or others are merely repeating "hearsay" on the patient's wishes, especially looking for newly purchased life insurance policies, etc.
If all is in order, then I guess it's a "go". If not, a court appointed guardian would be appointed to guarantee that the patient receives appropriate care. The GAL would then be out of the picture.
I know, the last thing this world needs is more ambulance chasers, but if this had been done for Terri, she'd be in better shape. There are others in her situation being murdered for financial gain, and even to cover up a crime.