KRIVOSHA, C. J.

This matter comes before the court on error proceedings brought by the County Attorney of York County, Nebraska, pursuant to the provisions of sections 29-2315.01 and 29-2319(3), R.R.S. 1943. The specific question concerns the constitutionality of section 39-669, R.R.S. 1943, which provides as follows: "Any person who operates a vehicle in a manner so as to endanger or be likely to endanger any person or property shall be guilty of careless driving." (Emphasis supplied.) The county court of York County, Nebraska, wherein the appellee was tried on an amended charge of careless driving, sustained appellee's motion to dismiss the charge, finding section 39-669, R.R.S. 1943, was void for vagueness and therefore in violation of the fundamental constitutional requirements of the due process clause. On appeal the District Court for York County, Nebraska, also found the statute to be vague and in violation of the constitutional requirements applicable thereto, and ruled the statute unconstitutional. We agree with the District Court and affirm the judgment.

It is without question that a violation of section 39-669, R.R.S. 1943, constitutes a crime for which a perpetrator is subject to criminal prosecution. State v. Knoles, 199 Neb. 211, 256 N.W.2d 873. Since the statute in question is criminal in nature, it is a fundamental requirement of due process of law that such criminal statute be reasonably clear and definite. Markham v. Brainard, 178 Neb. 544, 134 N.W.2d 84; State v. Adams, 180 Neb. 542, 143 N.W.2d 920.

A crime must be defined with sufficient definiteness and there must be ascertainable standards of guilt to inform those subject thereto as to what conduct will render them liable to punishment thereunder. State v. Nelson, 168 Neb. 394, 95 N.W.2d 678; Heywood v. Brainard, 181 Neb. 294, 147 N.W.2d 772. The dividing line between what is lawful and unlawful cannot be left to conjecture. State v. Adams, supra; State v. Nelson, supra. The citizen cannot be held to answer charges based upon penal statutes whose mandates are so uncertain that they will reasonably admit of different constructions. A criminal statute cannot rest upon an uncertain foundation. The crime and the elements constituting it must be so clearly expressed that the ordinary person can intelligently choose in advance what course it is lawful for him to pursue. Penal statutes prohibiting the doing of certain things and providing a punishment for their violation should not admit of such a double meaning that the citizen may act upon one conception of its requirements and the courts upon another. State, ex rel. English v. Ruback, 135 Neb. 335, 281 N.W. 607; Connally v. General Construction Co., 269 U.S. 385, 46 S.Ct. 126, 70 L.Ed. 322. A statute which forbids the doing of an act in terms so vague that men of common intelligence must necessarily guess as to its meaning, and differ as to its application, violates the first essential element of due process of law. State v. Adams, supra; State v. Pocras, 166 Neb. 642, 90 N.W.2d 263.

In the case of State v. Adams, supra, this court was called upon to determine the constitutionality of section 39-7,108.01, R.R.S. 1943. We there held that the statute in question was sufficiently vague as to violate the constitutional requirements saying: "As pointed out by the defendant, in a broad sense the mere operation of a motor vehicle endangers the safety of others to some extent. Although it is unlikely that the Legislature intended such a broad application, there is no language in the statute which limits it to a more specific application."

The statute in question makes it a violation not only to operate a motor vehicle "in a manner so as to endanger * * * any person or property," but likewise makes it an equal violation to operate a motor vehicle "in a manner * * * likely to endanger any person or property." (Emphasis supplied.) If, in fact, as we said in State v. Adams, supra, men of common intelligence cannot ascertain in advance when they are operating a motor vehicle in a manner so as to endanger any person or property, all the more must it be said that it would be difficult or at least open to sufficient conjecture as to when one was operating a motor vehicle "in a manner so as to * * * be likely to endanger any person or property * * *" (Emphasis supplied.) Obviously the question of whether one is operating a motor vehicle in a manner so as to be likely to endanger must of necessity involve opinion and therefore be open to conjecture. Likewise, whether one is "likely" to be operating a motor vehicle in such a manner as to endanger any person or property may to some extent depend upon the ability of the driver as well as conditions, known or unknown, to the driver.

The determination as to whether the particular driving was, in fact, in a manner "likely" to endanger may in some instances be ascertainable only after the fact. The standard announced in the statute fails to describe a crime and the elements constituting the crime in a clear, prospective manner as required by our criminal law. There appears within the statute no ascertainable standard by which men of common intelligence can determine what is unlawful. Under the provisions of the act as it now stands, no injury need occur. The test is only to determine if, in fact, one operated an automobile in such a manner "likely" to endanger. In certain instances that may only be ascertainable after the fact and based upon speculation and conjecture. To permit the doing of an act without violation of the statute if performed by an experienced driver, while making the same act unlawful if performed by a novice driver, is far too vague and indefinite to withstand constitutional attack. We, therefore, find and declare that section 39-669, R.R.S. 1943, is vague and indefinite and is thus unconstitutional. We accordingly affirm the judgment of the District Court for York County, Nebraska

AFFIRMED.

McCOWN and BRODKEY, JJ., concur in result.