The developmentally disabled, specifically those mentally incompetent from birth, are entitled to a full panoply of constitutional rights and protections. These rights include the right to terminate life-sustaining treatment, the right of procreative integrity and the right not to be involuntarily institutionalized. However, the mentally incompetent developmentally disabled are generally unable to exercise these rights. This Note asserts first that proper procedural safeguards are necessary to guarantee the exercise of these constitutional rights by the incompetent disabled individual. Second, the Note focuses upon how best to preserve the disabled person's autonomy. The Note subsequently rejects the substituted judgment standard as a legal fiction, and endorses the best interest test which necessarily comports with the evidence, and properly accounts for the disabled person's incompetency.