The Quinlan case was very different, IIRC. Specific instructions left, and she was on a respirator. They took off the respirator, and she survived for quite some time thereafter. Cruzan was more similar, since it involved a feeding tube, but, again, specific intent was there.
There is so much doubt in this case as to the patients wishes that to remove the tube is clearly murder for the sake of convenience. The slippery slope of Quinlan and Cruzan is what brought us to this point, despite assurances that concerns about that very thing were dismissed as hysteria at the time.
Beyond the outrage and grief about Mrs. Schiavo, I have grave concerns about how much farther down the same slope this will take us. Dr. Kevorkian may be proven to be a prophet as well as a devil.
Please read my post # 199.