Neb. Rev. Stat. § 84-913.04

(1) A person who has served as investigator, prosecutor, or advocate in a contested case or in its prehearing stage may not serve as hearing officer or assist or advise a hearing officer in the same proceeding except as provided in subsection (3) of this section. (2) A person who is subject to the authority, direction, or discretion of one who has served as investigator, prosecutor, or advocate in a contested case or in its prehearing stage may not serve as hearing officer or assist or advise a hearing officer in the same proceeding except as provided in subsection (3) of this section. (3) If all parties consent, a person who has served as, or who is subject to the authority, direction, or discretion of one who has served as, investigator, prosecutor, or advocate in a contested case or in its prehearing stage may assist a hearing officer in the preparation of orders. (4) A person who has participated in a determination of probable cause or other equivalent preliminary determination in a contested case may serve as hearing officer or assist or advise a hearing officer in the same proceeding. (5) A person may serve as hearing officer at successive stages of the same contested case.