Penal Code section 2901 requires a person convicted of a sex offense to register with law enforcement authorities as a convicted sex offender. The registration must be updated within five working days of the offender’s birthday. (§ 290, former subd. (a)(1)(C), nowsubd. (a)(1)(D).) If the sex crime that gave rise to the registration requirement *362was a felony, a “willful” failure to update the registration is also a felony. (Id., subd. (g)(2).)
I disagree with the majority’s holding that an offender who inadvertently is one day late in updating his already registered address has willfully violated section 290.
I
Twenty-five years ago, defendant was convicted of three forcible sex offenses, for which he was sentenced to prison and ordered to register as a sex offender for the rest of his life.
In the year 2000, defendant was living in San Mateo at Project 90, a rehabilitation project for alcohol and drug abusers. He had registered with the San Mateo Police Department, giving Project 90 as his address. Because his birthday was March 5, he was statutorily required to update his registration by March 10, the fifth working day after his birthday. He did not do so. On the morning of March 13, which was a Monday and the first working day after the time to update his registration expired, a San Mateo police officer called Project 90 and left a recorded message asking to speak to defendant. Defendant returned the call in 15 minutes and appeared at the police station within an hour. He said he had forgotten to update his registration.
Although defendant was only a day late in updating his registration, he was arrested and charged with violating section 290. At trial, the jury submitted this question during its deliberations: “Is forgetting to regester [sic] a ‘willfull’ [¿7c] act according to the law.” The trial court responded that “forgetting to register by itself does not provide a defense to a charge of willful failure to register.” The jury convicted defendant of violating section 290. Because of defendant’s prior, felony convictions, the trial court could have sentenced him to 25 years to life under the “Three Strikes” law. Instead, the court struck all but one of his prior convictions and sentenced him to nine years in prison.
n
Subdivision (g)(2) of section 290 provides that with exceptions not relevant here, “any person who is required to register under this section based on a felony conviction . . . who willfully violates any requirement of this section ... is guilty of a felony . . . .” (Italics added.) At issue is whether a defendant who initially knew of the duty to update the registration within five working days of his or her birthday, but who forgets to do so in that period, has willfully violated section 290.
*363Pertinent here is People v. Garcia (2001) 25 Cal.4th 744 [107 Cal.Rptr.2d 355, 23 P.3d 590] (Garcia). There, the defendant argued that for an offender to “willfully” violate section 290 the offender must have actual knowledge of the duty to do so. This court unanimously2 agreed.
Unlike the defendant in Garcia, who claimed he never learned of the duty to register, defendant here admits he knew he had to update his registration but says he forgot he had to do so within the requisite five days after his birthday. Although Garcia is factually distinguishable, its reasoning is dis-positive here. Garcia explained: “Logically one cannot purposefully fail to perform an act without knowing what act is required to be performed. As stated in People v. Honig (1996) 48 Cal.App.4th 289, 334 [55 Cal.Rptr.2d 555], ‘the term “willfully” . . . imports a requirement that “the person knows what he is doing.” ’ ” (Garcia, supra, 25 Cal.4th at p. 752, italics added.)
Forgetting to do something means an inadvertent failure to do something. That is the opposite of a purposeful or willful failure to act. “The word ‘willfully,’ when applied to the intent with which an act is done or omitted, implies simply a purpose or willingness to commit the act, or make the omission referred to.” (§ 7.) A “willful” omission to perform a duty imposed by law, such as the duty to register as a sex offender, is an intentional omission, not an omission caused by negligence, inadvertence, or forgetfulness. (See, e.g., Boags v. Municipal Court (1987) 197 Cal.App.3d 65, 71 [242 Cal.Rptr. 681] [a public officer’s “willful omission” to perform a legal duty means “a willing intentional omission” to perform the duty].) A willful act is one done “ ‘intentionally or purposely as distinguished from accidentally or negligently ....’” (Black’s Law Dict. (7th ed. 1999) p. 1593, quoting Perkins & Boyce, Criminal Law (3d ed. 1982) pp. 875-876.) Here, defendant’s inadvertent failure to register timely was unquestionably negligent, but it was not willful.
III
Section 290 is a regulatory offense. (Maj. opn., ante, at p. 354; see also Wright v. Superior Court (1997) 15 Cal.4th 521, 527 [63 Cal.Rptr.2d 322, 936 P.2d 101].) Such offenses often require a degree of culpability that is less than the criminal negligence customarily required for conviction of a crime. This court has “assumed” that regulatory offenses with such reduced culpability levels “are constitutionally permissible where the purpose is to protect public *364health and safety and the penalties are relatively light.” (People v. Simon (1995) 9 Cal.4th 493, 521 [37 Cal.Rptr.2d 278, 886 P.2d 1271], italics added.)
But the penalties for violating section 290’s registration requirements are anything but light. Many sex offenders charged with failing to update their registration have two or more prior convictions that qualify as “strikes” under the Three Strikes law (§§ 667, subds. (b)-(f), 1170.12), because most sex offenses are strikes (see §§ 667.5, subd. (b) [listing crimes qualifying as strikes], 1192.7, subd. (c) 94 [same]), and because even a single sexual assault involving a single victim often results in convictions on multiple counts, each of which is a strike (see generally People v. Harrison (1989) 48 Cal.3d 321 [256 Cal.Rptr. 401, 768 P.2d 1078]). Thus, many violators of section 290 face sentences of 25 years to life under the Three Strikes law. To impose such a sentence on defendants who inadvertently fail to timely update their registrations, a degree of culpability below that of criminal negligence, may violate the state Constitution’s prohibition of cruel or unusual punishment (Cal. Const., art. I, § 17) or the federal Constitution’s prohibition of cruel and unusual punishment (U.S. Const., 8th Amend.).3
When a statute is susceptible to two constructions, one of which raises serious constitutional questions, courts construe the law to avoid such questions. (People v. Superior Court (Romero) (1996) 13 Cal.4th 497, 509 [53 Cal.Rptr.2d 789, 917 P.2d 628].) Therefore, I would construe the term “willfully” in section 290 as not applying to a convicted sex offender who inadvertently does not register timely with the police.
IV
In holding that forgetting to update registration as a convicted sex offender is a willful violation of section 290, the majority relies on a Court of Appeal decision, People v. Cox (2002) 94 Cal.App.4th 1371 [115 Cal.Rptr.2d 123], Quoting Cox, the majority states: “ ‘A spouse may forget a wedding anniversary, a patient a medical appointment; such lapses arise not from a lack of actual knowledge but a failure to respond to cues. Persons keep calendars and appointment books, ask others to remind them of duties and obligations and *365tie strings around their fingers all to insure that important responsibilities are met. We conclude that within this context one willfully fails to register when possessed of actual knowledge of the requirement he or she forgets to do so.’ ” (Maj. opn., ante, at p. 352.)
In response, I quote the observation by the dissenting Court of Appeal justice in this case: “One who forgets to do something—such as celebrate a wedding anniversary, or keep a medical appointment, using the examples in Cox—does not willfully insult their spouse or willfully stand up their doctor. Whatever the consequences of such an inadvertent omission may be, if one has forgotten, the omission is not willful.”
The majority fears that, unless inadvertently failing to register is treated as a violation of section 290, offenders who choose not to register will falsely claim they forgot to do so, thus making it hard for prosecutors to prove their guilt. (See maj. opn., ante, at pp. 357-358.) Such a claim, however, will succeed only if the jury believes it. Jurors are notoriously reluctant to attach great credibility to the testimony of convicted sex offenders. Also, the longer the delay in registering, the less credible the claim of “I forgot” becomes.
When, as here, the offender was only one day late in updating the registration, it may indeed be more difficult to establish that the violation was willful under section 290. Why shouldn’t it be? It may be just as difficult to prosecute for willful tax evasion a taxpayer who is one day late in filing a mandatory tax return. (See 26 U.S.C. § 7203 [a person who “willfully” fails to pay taxes is guilty of a misdemeanor].) In this case, defendant’s claim that he forgot to update his registration was highly credible: He was working as a house manager at Project 90, he responded immediately to the telephone call from the police, and he was only one day late in updating his registration. At sentencing, the trial court found that there was no evidence that defendant had deliberately tried to conceal his whereabouts from the police.
The majority’s holding defeats the purpose of section 290’s registration requirement, which is “to assure that persons convicted of the crimes enumerated therein shall be readily available for police surveillance at all times because the Legislature deemed them likely to commit similar offenses in the future.” (Barrows v. Municipal Court (1970) 1 Cal.3d 821, 825-826 [83 Cal.Rptr. 819, 464 P.2d 483].) As a result of the majority’s holding, a person who genuinely forgets to register on time is likely to go into hiding to avoid arrest, particularly when facing, like defendant here, a sentence of 25 years to life under the Three Strikes law. In making it more difficult to track down these offenders, the majority has frustrated the Legislature’s goal of making those individuals “readily available for police surveillance at all times.” (Ibid.)
*366Conclusion
That people may forget to do things they sincerely want and intend to do is a matter of common experience. Forgetting cannot be willed; it is an unplanned malfunction of the conscious mind. For this reason, a person who intends to do something, but forgets to do it, has not willfully failed to do that thing. Thus, I disagree with the majority that a person may commit the criminal offense of “willfully” violating the sex offender registration law-—a crime for which a defendant may spend the rest of his life in prison-—by mere forgetfulness.
I would reverse the judgment of the Court of Appeal.
Appellant’s petition for a rehearing was denied September 29, 2004. George, C. J., did not participate therein. Kennard, J., was of the opinion that the petition should be granted.
All further statutory citations are to this code.
Although I authored a concurring and dissenting opinion in Garcia, I disagreed only with the majority’s conclusion that the instructional error in that case was harmless. (Garcia, supra, 25 Cal.4th at pp. 759-762 (conc. & dis. opn. of Kennard, J.).)
In People v. Carmony (2004) 33 Cal.4th 367 [14 Cal.Rptr.3d 880, 92 P.3d 369], the defendant was convicted of violating section 290 and sentenced to a term of 25 years to life in prison based on his failure to update his registration as a sex offender within five days of his birthday, which the defendant claimed was inadvertent. After addressing other unrelated issues, this court remanded the case to the Court of Appeal to consider the defendant’s contention that his sentence violated the state and federal Constitutions’ prohibitions against cruel and/or unusual punishment. (Id. at p. 380, fn. 6.) The question whether the defendant’s sentence violated those constitutional provisions was not before this court in Carmony. Nor was the question at issue here: the meaning of the term “willfully” as used in section 290.