446 N.W.2d 224 STATE OF NEBRASKA, APPELLEE, v. KEVIN D. GERDES, APPELLANT. No. 88-973.Supreme Court of Nebraska. Filed September 29, 1989. 1. Judgments: Collateral Estoppel. The doctrine of collateral estoppel means that when an issue of ultimate fact has once been determined by a valid and final judgment, the issue cannot again be litigated between […]