In trials for conspiracy, in cases where an overt act is required by law to consummate the offense, no conviction shall be had unless one or more overt acts be expressly alleged in the indictment, nor unless one or more of the acts so alleged be proved on trial; but other overt acts not alleged in the indictment may be given in evidence on the part of the prosecution.
Neb. Rev. Stat. §§ 29-2014