Nebraska Revised Statute 27-501
Rule 501. Privileges recognized only as provided.
Except as otherwise required by the Constitution of the United States or the State of Nebraska or provided by Act of Congress, or the Legislature of the State of Nebraska, by these rules or by other rules adopted by the Supreme Court of Nebraska which are not in conflict with laws governing such matters, no person has the privilege to:
(1) Refuse to be a witness; or
(2) Refuse to disclose any matter; or
(3) Refuse to produce any object or writing; or
(4) Prevent another from being a witness or disclosing any matter or producing any object or writing.
An expert witness retained by one party may be compelled or will be allowed to testify to a matter of opinion upon request of the opposing party. IAFF Local 831 v. City of No. Platte, 215 Neb. 89, 337 N.W.2d 716 (1983).