The doctrine of the intent as it prevails in the criminal law, is necessarily one of the foundation principles of public justice. There is only one criterion by which the guilt of man is to be tested. It is whether the mind is criminal. Criminal law relates only to crime. And neither in philosophical speculation, nor in religious or moral sentiment, would any people in any age allow that a man should be deemed guilty unless his mind was so. It is, therefore, a principle of our legal system, as probably it is of every other, that the essence of an offense is the wrongful intent without which it can not exist. (1 Bishop's Crim. Law, § 287.)
Again, the same author, writing on the subject of knowledge, as necessary to establish the intent, says:
It is absolutely necessary to constitute guilt, as in indictments for uttering forged tokens, or other attempts to defraud, or for receiving stolen goods, and offenses of a similar description. (1 Crim. Prac. § 504.)
In regard to the offense of obtaining property by false pretenses, the author says:
The indictment must allege that the defendant knew the pretenses to be false. This is necessary upon the general principles of the law, in order to show an offense, even though the statute does not contain the word "knowingly." (2 Id. § 172.)
As to a presumed knowledge of the law, where the fact involves a question of law, the same author says:
The general doctrine laid down in the foregoing sections (i.e., that every man is presumed to know the law, and that ignorance of the law does not excuse), is plain in itself and plain in its application. Still, there are cases, the precise nature and extent of which are not so obvious, wherein ignorance of the law constitutes, in a sort of indirect way, not in itself a defense, but a foundation on which another defense rests. Thus, if the guilt or innocence of a prisoner depends on the fact to be found by the jury, of his having been or not, when he did the act, in some precise mental condition, which mental condition is the gist of the offense, the jury in determining this question of mental condition, may take into consideration his ignorance or misinformation in a matter of law. For example, to constitute larceny, there must be an intent to steal, which involves the knowledge that the property taken does not belong to the taker; yet, if all the facts concerning the title are known to the accused, and so the question is one merely of law whether the property is his or not; still he may show, and the showing will be a defense to him against the criminal proceeding, that he honestly believed it his through a misapprehension of the law.
