The U.S. Supreme Court affirmed, in a technical sense, the Missouri Supreme Court's decision by arguing that the states were relatively free to set whatever evidentiary standards they thought appropriate to safeguard the state's legitimate interest in preserving life. As such, while it did not endorse Missouri's "clear and convincing evidence" standard as the right criterion to use, it did endorse it as an acceptable standard in cases such as the one before it, where the patient is unable to speak for him- or herself. At the same time, and for the first time, the U.S. Supreme Court articulated the existence of a constitutionally protected "liberty" interest (found both in common law and in the 14th Amendment of the U.S. Constitution) that includes the right to refuse life-sustaining medical treatment, including tube feeding. Thus, while the states are free to set standards of evidence they will require regarding what an incompetent patient's wishes would be, they are not free to limit the substance of the right (for example, by summarily excluding tube feeding as something that can be withheld or withdrawn).