755 ILCS 9/15

(a) All adults are presumed to be capable of making decisions regarding daily living and to have capacity unless otherwise determined by a court. A diagnosis of mental illness, intellectual disability, or developmental disability, of itself, does not void the presumption of capacity. (b) The manner in which an adult communicates with others is not grounds for deciding that the adult is incapable of managing the affairs of the adult. (c) The execution of a supported decision-making agreement may not be used as evidence of capacity or incapacity in any civil or criminal proceeding and does not preclude the ability of the adult who has entered into a supported decision-making agreement to act independently of the agreement.