Whether assistant district attorneys have authority to deny exculpatory evidence

QUESTION(S) PRESENTED Would assistant district attorney have authority to deny exculpatory evidence brought to his office? Do deputies have authority to say someone who has admitted to consuming alcohol is a creditable witness ? Do deputies have authority to ask someone under the influence for consent to search and seize when all signs show they are clearly moving from a residents they do not own? . Do deputies have authority to question a minor child without consent of the parent when a parent is present?