Ladd, J.
The indictment charged that the defendant “did unlawfully and willfully resist and oppose one L. W. Harris, a deputy sheriff of Hardin county, Iowa, in serving and attempting to serve a certain search warrant.” On the trial the accused objected to, the introduction of evidence because of the insufficiency of the indictment, and based a motion in arrest of judgment on the same ground. The statute under which the indictment was returned provides that “'if any person knowingly and willfully resist or oppose any officer of this state, or any person authorized by law, in serving or attempting to serve any legal writ, rule, order or process whatsoever,” he shall be punished accordingly. Code, section 4899. It will be observed that “unlawfully” was inserted in the indictment instead of “knowingly,” used in *354tbe statute. As tbe word “unlawfully” formed no part of tbe description of tbe offense, it was superfluous and added notbing. State v. Capps, 4 Iowa, 502. It did not supply tbe omission of “knowingly.” An act may be knowingly done, and yet be unlawful, or it may be unlawful tbougb done in ignorance. State v. Stalls, 37 Texas, 440; State v. Arnold, 39 Texas, 74. It was not enough, to constitute tbe offense, to charge, tbe opposition or resistance to bave been willful. It must also bave been with knowledge tbat tbe person resisted or opposed was an officer. Such an averment was essential at common law. State v. Downer, 8 Vt. 428; State v. Hilton, 26 Mo. 199; Kernan v. State, 11 Ind. 471; Com. v. Kirby, 2 Cush. 577; State v. Maloney, 12 R. I. 251. Our statute is, in, this respect simply a statement of tbe law as it formerly stood. But tbe state urges that “knowingly” and “willfully” are synonymous, and tbat tbe omission of tbe former detracted notbing from tbe meaning of tbe indictment. To willfully do an act implies tbat it be done by design or with set purpose. One might purposely do an act which would bave tbe effect of impeding an officer in tbe performance of bis duties, in entire ignorance of tbe capacity in which such officer was acting. Tbe obstruction denounced is tbat, not only designedly or purposely interposed, but with knowledge tbat tbe person hindered was at tbe time an officer serving or attempting to serve some writ, rule, order, or process. This results from giving tbe words of tbe statute their usual meaning, such as contemplated by tbe lawmakers. In this case it was charged tbat certain bottles of beer were destroyed by tbe defendant. As they belonged to him, he bad a right to willfully break them, unless in doing so be interfered with tbe serving of tbe search warrant. But if be knew Harris, as an officer of tbe law, bad taken tbe beer under tbe search warrant, and was preserving it as required, or was about to do, so, and yet, with this knowledge, purposely spilled it on tbe ground, then be was guilty, under tbe statute, of opposing tbe officer. In *355other words, the facts of this case demonstrate the necessity of alleging knowledge. See Harrington v. State, 54 Miss. 493.
The indictment was sufficient in other respects. It clearly alleged what the officer was doing, and the particular acts of obstruction. State v. Maloney, supra. — Reversed.