Neb. Rev. Stat. § 29-1819: Pleas of guilty, not guilty, or nolo contendere; when required; failure to plead; effect.

If the issue on the plea in bar be found against the defendant, or if upon arraignment the accused offers no plea in bar, he shall plead guilty, not guilty, or nolo contendere; but if he pleads evasively or stands mute, he shall be taken to have pleaded not guilty.