A federal law, the National Firearms Act, prohibits the possession of an unregistered “machinegun.” (26 U.S.C. *889§ 5845(a)(6).) California’s Assault Weapons Control Act prohibits possession of an unregistered “assault weapon.” (Pen. Code, § 12280.) Both laws carry a potential prison sentence. Both laws are silent on the mental state required for a violation.
In Staples v. United States (1994) 511 U.S. 600 [114 S.Ct. 1793, 128 L.Ed.2d 608] (Staples), the United States Supreme Court held that unlawful machinegun possession under-the federal act required proof that the accused knew that a firearm had the requisite characteristics of a machinegun. Likewise, I conclude that unlawful assault weapon possession under the California act requires proof that the accused knew the firearm had the requisite characteristics of an assault weapon.
The majority, by contrast, holds that someone who lacks any actual knowledge that a firearm has such characteristics can nevertheless be convicted of unlawfully possessing an assault weapon. The majority does so by injecting into this criminal case a concept of civil law, namely, the negligence standard in torts, which asks whether wrongdoers “should have known” of harm resulting from their conduct.
The majority’s test casts too wide a net, snaring persons who lack the culpability appropriate for imposing a state prison sentence. I cannot agree that the Legislature intended such an unfair test. I therefore dissent.
I
Enacted by our Legislature in 1989, the Assault Weapons Control Act defines as “assault weapons” certain semiautomatic rifles, pistols, and shotguns, listing them by make and model. (Pen. Code, § 12276.)1 As relevant here, one of the listed firearms is the “SKS with detachable magazine.” (§ 12276, subd. (a)(ll).) A person who lawfully possessed an assault weapon before June 1, 1989, could register it with the state Department of Justice by a specified date. (§ 12285, subds. (a) and (f).) Although it is legal to possess and use a registered assault weapon for a variety of purposes (see § 12285, subd. (c)), possession of an unregistered assault weapon is a crime punishable “by imprisonment in the state prison, or in a county jail, not exceeding one year” (§ 12280, subd. (b)).
II
After admitting possession of a controlled substance, 16-year-old Jorge M. (the minor) was made a ward of the juvenile court. The court granted *890probation on conditions, among others, that the minor “not have any dangerous or deadly weapons” and that he “submit to search and seizure.” Shortly thereafter, the police, accompanied by a probation officer, searched the minor’s house and seized several rifles. The minor was charged with possessing firearms in violation of his probation (§ 12021, subd. (d)) and possessing an unregistered assault weapon (§ 12280, subd. (b), hereinafter section 12280(b)).
Probation officer Brian Tsubokawa testified that upon entering the house he asked the minor where he kept his “personal items,” and the minor “pointed over to the bunkbed area” in a makeshift bedroom situated behind the kitchen. According to Officer Manuel Ramirez, a member of the Los Angeles Police Department’s gang abatement unit, the minor said the top bunk was his. From that bunk, Ramirez seized three unloaded rifles; from the top of a nearby clothes cabinet, he recovered a fourth rifle together with an empty “banana clip,” a type of detachable magazine. The latter firearm bore the markings “SKS-45” and was configured to accept a detachable magazine; it had never been registered as an assault weapon.
The minor’s 22-year-old brother, Juan, testified that he, not the minor, slept on the top bunk in the makeshift bedroom. In the area where the lower bunk normally would be, Juan stored boxes. The minor slept on the floor of their sisters’ bedroom. The rifles belonged to Juan and their father, an avid hunter, and were normally kept in a closet. Juan had removed the firearms from the closet to take them to a relative’s house for safekeeping during the family’s planned visit to Mexico to attend Juan’s wedding. The mother and the minor corroborated Juan’s testimony. The police found eight other rifles belonging to the minor’s father elsewhere in the house.
The trial court sustained the charges, crediting the testimony of probation officer Tsubokawa that the minor had indicated he kept personal items in the bunk bed area where Officer Ramirez found the four rifles. The Court of Appeal reversed the assault weapons charge but sustained the charge of possessing firearms in violation of probation. The court found the evidence sufficient on the issue of the minor’s constructive possession of the SKS rifle recovered from the makeshift bedroom to which the minor had immediate access. But the court concluded there was no evidence the minor knew the firearm had the “characteristics which brought it within the statutory definition of an assault weapon.” Such knowledge, the court held, was an element of the offense. We granted the People’s petition for review to determine the propriety of the Court of Appeal’s holding.
Ill
Firmly embedded in Anglo-American criminal jurisprudence is the notion that criminal liability for a prohibited act requires a guilty or wrongful *891purpose. (United States v. United States Gypsum Co. (1978) 438 U.S. 422, 436 [98 S.Ct. 2864, 2873, 57 L.Ed.2d 854].) In California, this principle is codified in section 20, enacted in 1872. It states: “To Constitute Crime There Must Be a Unity of Act and Intent. In every crime or public offense there must exist a union, or joint operation of act and intent, or criminal negligence.” Thus, under California law criminal liability rests not just on wrongful conduct, but on wrongful conduct coupled with one of two culpable mental states, either wrongful intent or criminal negligence.2
Wrongful intent requires either a conscious desire of a particular result or knowledge that the result is a practical certainty. (1 LaFave & Scott, Substantive Criminal Law (1986) § 3.5(a), pp. 303-304.) “So basic is this requirement that [wrongful intent] is an invariable element of every crime unless excluded expressly or by necessary implication.” (People v. Vogel (1956) 46 Cal.2d 798, 801 [299 P.2d 850].) As the United States Supreme Court explained in Morissette v. United States (1952) 342 U.S. 246, 250 [72 S.Ct. 240, 243, 96 L.Ed. 288]: “The contention that an injury can amount to a crime only when inflicted by intention is no provincial or transient notion. It is as universal and persistent in mature systems of law as belief in freedom of the human will and a consequent ability and duty of the normal individual to choose between good and evil.”
Criminal negligence, on the other hand, is a mental state rarely selected by legislatures as an element of a crime. It exists when an act, although unintended, is “ ‘ “aggravated, culpable, gross, or reckless, that is, . . . such a departure from what would be the conduct of an ordinarily prudent or careful [person] under the same circumstances as to be incompatible with a proper regard for human life.” ’ ” (People v. Sargent (1999) 19 Cal.4th 1206, 1215 [81 Cal.Rptr.2d 835, 970 P.2d 409], quoting People v. Penny (1955) 44 Cal.2d 861, 879 [285 P.2d 926].) This aggravated conduct sets criminal negligence apart from civil negligence, which is conduct inconsistent with that of a reasonable person in like or similar circumstances and does not require aggravated, gross, or reckless behavior. (Prosser & Keeton on Torts (5th ed. 1984) § 32, p. 175; see Cheong v. Antablin (1997) 16 Cal.4th 1063, 1075 [68 Cal.Rptr.2d 859, 946 P.2d 817] (cone. opn. of Kennard, J.).)
Under this latter standard, a pertinent inquiry is whether persons “knew or should have known” a particular set of facts that make their conduct unreasonable. (Carlin v. Superior Court (1996) 13 Cal.4th 1104, 1112, fh. 2 [56 Cal.Rptr.2d 162, 920 P.2d 1347].) Until today, no decision of this court *892has held that someone can be prosecuted under a criminal law that contains no express mental state requirement, based merely on the person’s civil negligence.
The final category of offenses, those imposing strict liability, requires neither intent nor any form of negligence. (See 1 LaFave & Scott, Substantive Criminal Law, supra, § 3.8, p. 340 et seq.) As this court has explained: “The [United States] Supreme Court has indicated that regulatory or ‘public welfare’ offenses which dispense with any mens rea, scienter, or wrongful intent element are constitutionally permissible, but it has done so on the assumption that the conduct poses a threat to public health or safety, the penalty for those offenses is usually small, and the conviction does not do ‘grave damage to an offender’s reputation.’” (People v. Simon (1995) 9 Cal.4th 493, 519 [37 Cal.Rptr.2d 278, 886 P.2d 1271]; People v. Vogel, supra, 46 Cal.2d at p. 801, fn. 2.)
IV
With this background in mind, I now turn to the question of what the Legislature intended in section 12280(b), which sets forth no mental state requirement. I noted earlier that wrongful intent, the ordinary standard for criminal liability, is the required mental state for most crimes. As I explained, this intent has been defined as the conscious desire that one’s actions cause a particular result or the knowledge that the result is a practical certainty. For certain possessory crimes, this wrongful intent requires knowledge not only that the contraband item is present but also of the item’s characteristics that make its possession unlawful. (See People v. Prochnau (1967) 251 Cal.App.2d 22, 30 [59 Cal.Rptr. 265].) There is, however, no requirement of knowledge that the law prohibits possession of the item. (§ 7, par. 5.)
California case law has not been consistent on whether knowledge is required under statutes that, in defining a possessory offense, do not mention any mental state. (Compare People v. Williams (1971) 5 Cal.3d 211, 215 [95 Cal.Rptr. 530, 485 P.2d 1146] [knowledge of narcotic character of the item possessed is essential element of possessing controlled substance] with People v. Corkrean (1984) 152 Cal.App.3d 35, 37-41 [199 Cal.Rptr. 375] [knowledge that gun automatically fires more than one shot not element of law prohibiting possession of a machinegun] and People v. Harrison (1969) 1 Cal.App.3d 115, 120 [81 Cal.Rptr. 396] [knowledge that firearm is loaded not an element of offense of carrying a loaded firearm].)
Of particular assistance here is the United States Supreme Court’s recent decision in Staples, supra, 511 U.S. 600. That case involved a federal *893firearms law that, like the California firearms law in this case, contained no express mens rea requirement. To determine whether Congress intended the defendant to “know the facts that make his conduct illegal,” or intended instead to create a strict liability offense, the high court focused on two factors: The statute criminalized firearm possession, which the court described as “traditionally lawful conduct,” and it provided a potential 10-year prison sentence, which the court characterized as “a severe penalty.” (Staples, supra, 511 U.S. at pp. 605, 618-620 [114 S.Ct. at pp. 1797, 1803-1804].) These two circumstances led the court to conclude that Congress did not intend to create a strict liability offense and that therefore the defendant could not be guilty of the federal crime of possessing an unregistered machinegun unless he “knew of the features of his AR-15 that brought it within the scope of the [federal] Act.” (Id. at p. 619 [114 S.Ct. at p. 1804].)
Application in this case of the high court’s test in Staples, supra, 511 U.S. 600, compels the conclusion that our state Legislature did not intend the California firearms law at issue here to be a strict liability offense. As in Staples, the law criminalizes firearm possession, traditionally lawful conduct, and it imposes a severe penalty, a potential state prison sentence. The majority does not conclude otherwise. It observes: “[A] construction of section 12280(b) that dispenses completely with scienter may result in the severe punishment of innocent possessors, a result we do not believe the Legislature intended.” (Maj. opn., ante, at p. 884.)
But the majority rejects the high court’s further conclusion in Staples, supra, 511 U.S. 600, that a possessory offense that is not a strict liability crime and does not specify a mental state must require knowledge by the accused of the facts that make the act of possession illegal. The majority’s holding is at odds with two recent decisions of this court, People v. Coria (1999) 21 Cal.4th 868 [89 Cal.Rptr.2d 650, 985 P.2d 970] (Coria) and People v. Rubalcava (2000) 23 Cal.4th 322 [96 Cal.Rptr.2d 735, 1 P.3d 52] (Rubalcava). In both of these decisions, this court inferred an actual-knowledge requirement for possessory offenses that had no express mental state requirement.
In Coria, which involved the crime of manufacturing methamphetamine, we explained: “Simply stated, there is no reason in law or logic to construe [the statute] as a strict liability offense and thus permit the conviction of a person for manufacturing methamphetamine, a felony, for extracting pseudoephedrine from pills if the person does not know the extraction was performed for the purpose of, or as part of the process of, manufacturing methamphetamine. Merely engaging in chemical synthesis is not enough; the defendant must have knowledge of the facts which make the chemical *894synthesis unlawful, i.e., that methamphetamine is being manufactured.” (Coria, supra, 21 Cal.4th at p. 880, italics added.)
We further noted in Coria that a statute’s “silence with respect to a knowledge element does not mean the Legislature intended to dispense with the requirement” that the accused actually “know” the contraband character of the item possessed. (Coria, supra, 21 Cal.4th at p. 878.) Rather, for crimes carrying the possibility of “severe punishment” such as manufacturing methamphetamine, which is punishable by a state prison term of three, five, or seven years, the “ ‘usual presumption’ ” is that a defendant “ ‘must know the facts that make his conduct illegal.’ ” (Ibid., quoting Staples, supra, 511 U.S. at p. 619 [114 S.Ct. at p. 1804], italics added.)
Just two months ago, we applied this “usual presumption” in Rubalcava, supra, 23 Cal.4th 322, in holding knowledge to be an element of a dangerous weapons offense, that of carrying a concealed dirk or dagger, which is punishable by up to three years in state prison. To commit the offense, we said, “the defendant must knowingly and intentionally carry concealed upon his or her person an instrument ‘that is capable of ready use as a stabbing weapon,’ ” thus satisfying the statutory definition of a dirk or dagger. (Id. at p. 332, italics added.)
Applying the usual presumption of legislative intent as the high court did in Staples, supra, 511 U.S. 600, and as this court did in Coria, supra, 21 Cal.4th 868, and Rubalcava, supra, 23 Cal.4th 322, unlawful possession of an assault weapon, which carries a maximum three-year state prison sentence, requires knowledge by the defendant that the firearm has the characteristics that make it an assault weapon.
Disregarding this usual presumption, the majority injects into the offense of possession of an unregistered assault weapon a mental state taken from the civil law of torts: whether the accused “knew or reasonably should have known” the firearm possessed the characteristics that made it an assault weapon. (Maj. opn., ante, at p. 887, italics omitted.) That this is the test for civil negligence is not disputed by the majority (maj. opn., ante, at p. 887, fn. 11), which cites no decision by this court adopting this civil law standard as the requisite mental state in a criminal case.
Seeking to justify its novel imposition here of the civil negligence standard of culpability, the majority asserts that resort to this minimal standard is necessary to aid the prosecution in proving unlawful possession of an assault weapon. (Maj. opn., ante, at p. 885.) This assertion is both legally and factually dubious. Facilitating prosecution is not the goal of statutory interpretation, nor will requiring proof of actual knowledge unduly hamper prosecutions for unlawful assault weapons possession.
*895As the majority concedes, a defendant’s actual knowledge that a firearm has the attributes of an assault weapon can be proven circumstantially, typically by evidence of a defendant’s familiarity with firearms. (Maj. opn, ante, at p. 885.) The only prosecutions that are likely to be aided by the majority’s “should have known” standard are those of novice firearm owners, such as a widow who inherits her husband’s rifle that she has never fired or even handled. The majority’s holding will facilitate her prosecution. It may not have occurred to her to examine the rifle to determine its precise make and model, the characteristics making it an assault weapon. Yet, under the majority’s holding, she could now face felony conviction and state imprisonment because, in the majority’s view, those characteristics are something she “should have known.”
Like the Court of Appeal, I would hold that an element of the offense of possessing an unregistered assault weapon is actual knowledge by the accused that the firearm has the characteristics that make it an assault weapon. In this case, the prosecution did not prove such knowledge by the minor. Therefore, I would affirm the judgment of the Court of Appeal, reversing the assault weapons charge.
Baxter, J., concurred.
Appellant’s petition for a rehearing was denied September 20, 2000.
Further undesignated statutory references are to the Penal Code.
In accord with common practice, I use the terms “mental state” and “mens rea” to include forms of negligence and strict liability, which do not require proof of any subjective state of mind.