Neb. Rev. Stat. § 23-1711

The sheriff shall, whenever directed so to do in writing by the county attorney, make special investigation of any alleged infraction of the law within his county, and report with reference thereto within a reasonable time to such county attorney. When such investigation is made the sheriff shall file with the county clerk a detailed, sworn statement of his expenses, accompanied by the written order of the county attorney, and the board shall audit and allow only so much thereof as it shall find reasonable and necessary.