This case, as the majority states, presents the question whether forgetting to update one’s registration “because of severe depression" may negate the Penal Code section 290 (section 290) willfulness requirement. (Maj. opn., ante, at p. 68.) Without directly answering the stated question, the majority holds that “the willfulness element of the offense [of failure to register] may be negated by evidence that an involuntary condition—physical or mental, temporary or permanent— deprived a defendant of actual knowledge of his or her duty to register.” (Id. at p. 69.) I agree. The majority further holds that “[o]nly the most disabling of conditions . . . would qualify under the standard [it] announce[s] today.” (Ibid.) As an abstract principle, I agree. Certainly the condition must be sufficiently disabling so as to deprive the afflicted individual of his or her awareness or knowledge of the duty to register.
The majority, however, goes further. In an ipse dixit resolving the factual issue defendant never had the opportunity in the trial court to address, the majority declares: “Defendant’s claimed depression clearly did not satisfy this standard. Defendant knew of his obligation to register and, had he taken it to heart, he could have managed to discharge it” (Maj. opn., ante, at p. 69, italics added.) It is here I part company with the majority. I disagree that this court, in the circumstances of this case, where the trial court precluded defendant from presenting his proffered evidence of severe depression, can as a matter of law declare that defendant “knew” of his obligation to register. Rather, I agree with the Court of Appeal that the trial court abused its discretion in refusing to consider defendant’s proffer of evidence that he *76suffered from a clinical depression1 that caused him to fail to remember to register. Although, as the majority states, the question whether a defendant has proffered evidence sufficiently substantial to go to the jury under the standard the court announces today is a question confided to the sound discretion of the trial court (maj. opn., ante, at p. 73), here, contrary to the majority, the trial court did not exercise an informed discretion, evidently rejecting defendant’s proffer, instead, in the mistaken belief that evidence of mental impairment was legally irrelevant to the question of a defendant’s knowledge of the duty to register.
I
Section 290 requires persons convicted of enumerated sex crimes to register with appropriate law enforcement authorities. Subdivision (g)(2) of section 290 provides in pertinent part that “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.) Almost 50 years ago, the United States Supreme Court held that one’s constitutional right to due process of law requires, at a minimum, that a conviction for violating a criminal registration law include a showing of “actual knowledge of the duty to register or proof of the probability of such knowledge.” (Lambert v. California (1958) 355 U.S. 225, 229 [2 L.Ed.2d 228, 78 S.Ct. 240], italics added.)
We addressed the meaning of the term “willfully,” as used in section 290, in People v. Garcia (2001) 25 Cal.4th 744 [107 Cal.Rptr.2d 355, 23 P.3d 590] (Garcia). There we held that, in cases charging a violation of section 290, the jury must be instructed the word “willfully” requires that the accused have *77had actual knowledge of his duty to register. Subsequently, in People v. Barker (2004) 34 Cal.4th 345 [18 Cal.Rptr.3d 260, 96 P.3d 507] (Barker), we held that merely forgetting to register was not a defense to the crime of willfully failing to register. Barker specifically reserved judgment, however, on whether “an acute psychological condition, or a chronic deficit of memory or intelligence might negate the willfulness required for a section 290 violation.” (Id. at p. 358, italics omitted.)
The law requires that persons convicted of certain enumerated sex crimes be informed, upon release from confinement, of their duty to register (§ 290, subd. (b)(1)) and sign a form indicating they have been so informed (ibid.). At the outset, then, we assume all persons required to register had, at least at one time, the knowledge of their duty to do so. It is not, however, this preliminary knowledge that is relevant here. The crime defined in section 290 is the willful failure to register or reregister at any one of the numerous times set out in the statute. “The word ‘willfully’ implies a ‘purpose or willingness’ to make the omission. [Citation.] Logically one cannot purposefully fail to perform an act without knowing what act is required to be performed.” (Garcia, supra, 25 Cal.4th at p. 752, quoted with approval in Barker, supra, 34 Cal.4th at p. 351.) It is thus the offender’s knowledge or awareness of the duty at the time he or she fails to register that is relevant.
Although “just forgetting” one’s duty to register does not negate such knowledge (Barker, supra, 34 Cal.4th at p. 361), the majority accepts the proposition that certain psychological conditions can render a person unable to recall the legal duty to register. “Severe Alzheimer’s disease is one example that comes to mind; general amnesia induced by severe trauma is another.” (Maj. opn., ante, at p. 69.) Because sex offenders are told on release from prison of their legal duty to register, a trier of fact may infer that, in the normal case, when an offender fails to register, he or she did so with knowledge of the duty, rendering the offender’s omission a willful one. “A jury may infer knowledge from notice, but notice alone does not necessarily satisfy the willfulness requirement.” (Garcia, supra, 25 Cal.4th at p. 752.) Evidence of a qualifying mental illness is thus relevant to rebut the inference of knowledge.
II
Defendant proposed to present both lay and expert evidence that he suffered from severe depression. Thus, he offered the testimony of lay witnesses who would have testified that he was a friendly, hard-working, “happy-go-lucky” person who was involved in his community. In the months *78leading up to his failure to register in December 2001, however, he appeared depressed, unfocused and withdrawn. He had been financially unable to retain possession of his home of several years and had moved first into a friend’s garage and then to a new residence in Pacifica. His mother, with whom he was very close, had been battling cancer for the previous two years and had recently been diagnosed with a rapidly spreading form of the disease. During this time, defendant had been flying back and forth to New York to be with his mother. During this same period, defendant’s girlfriend decided to end their relationship, and the mother of his son was being uncooperative in permitting visitation. In addition, defendant’s constant companion for the previous 14 years, his pet German shepherd, Ruby, died in November 2001. A friend would have testified that the dog’s death had a “devastating effect” on defendant. More than one witness would have testified that, during this period, defendant lost a lot of weight and appeared forgetful.
In opposing the prosecution’s motion in limine to exclude his proffered evidence, defense counsel asserted he would call an expert witness (Dr. Weiner) who, if permitted, would testify that defendant showed signs of clinical depression and that such depression affected defendant’s concentration and memory.
In finding defendant’s proffered evidence was properly excluded, the majority dismisses the seriousness of his potential illness, characterizing his problem as one merely of lack of effort. For example, the majority asserts that defendant “simply claimed his depression made it more difficult for him to remember to register.” (See maj. opn., ante^ at p. 72.) Defendant and others with mental disabilities, says the majority; .must cope “as best they can.” (Ibid) The majority thus implies that unlike persons suffering from amnesia or Alzheimer’s disease who cannot remember their legal duty to register no matter how hard they try, one suffering a major depressive episode can remember if he or she simply tries harder to do so. The majority cites no authority in support of this suggestion. Indeed, the opposite appears to be true. According to the National Institute of Mental Health, “[a] depressive disorder is an illness that involves the. body, mood, and thoughts. It affects the way a person eats and sleeps, the way one feels about oneself, and the way one thinks about things. A depressive disorder is not the same as a passing blue mood. It is not a sign of personal weappess or a condition that can be willed or wished away. People with a depressive illness cannot merely ‘pull themselves together’ and get better. Without treatment, symptoms can last for weeks, months, or years.” (<http://www.nimh.nih.gov/publicat/depression.cfm> [as of June 23, 2005], italics added.)
*79The prevailing diagnostic tool for mental disorders explains that “[m]any individuals [suffering from a major depressive episode] report impaired ability to think, concentrate, or make decisions. [Citation.] They may appear easily distracted or complain of memory difficulties.” (Diagnostic and Statistical Manual of Mental Disorders (4th ed. 2000) p. 350 (DSM-IV-TR), italics added.) Defendant’s proffered evidence of his depressive mood and unfocused affect, his sudden weight loss and diminution of energy were all consistent with known symptoms of depression. (1 Encyclopedia of Mental Health, supra, at pp. 735-736; DSM-IV-TR, supra, at p. 356.) That he experienced a series of major life stressors during the period leading up to his failure to register is also consistent with his having endured a major depressive episode.2
We need not now conclude the trier of fact would or would not have been convinced by defendant’s proffered evidence. The question before us is one of admissibility. On its face, the evidence shows defendant experienced more than a “passing blue mood,” that he in fact suffered from serious depression at the time he failed to register, and that sufferers of such depressive episodes often experience significant memory deficits. I conclude this evidence, lay evidence that in turn supported an expert medical opinion, was relevant to the question of whether defendant’s failure to register was a willful omission as required by section 290.
III
The trial proceedings in this case took place on July 22, 2002, well before our decision in Barker, supra, 34 Cal.4th 345. Although the trial court anticipated our Barker decision by concluding that merely forgetting one’s duty to register was not a defense, the lower court could not have anticipated that we would limit our holding in Barker and expressly except “acute psychological condition[s]” affecting memory. {Id. at p. 358, italics omitted.) Instead, the trial court evidently excluded defendant’s proposed evidence of his depression on the ground the evidence was not relevant. Because I find such evidence was relevant, I would remand this case to the trial court to enable it to reassess the evidence’s admissibility under the proper standard. If, in fact, defendant suffered from a serious and diagnosable depressive disorder affecting his memory, his failure to register in this case may not have been willful as required by section 290.
*80Defendant, of course, has a constitutional right to present relevant evidence in his defense. To the extent, therefore, the majority declines to permit this defendant to present evidence he suffered from a serious depressive disorder that negated his knowledge of the duty to register, I dissent.
Moreno, J., concurred.
Appellant’s petition for a rehearing was denied July 27, 2005. Werdegar, J., was of the opinion that the petition should be granted.
“Major depression is the most common of the mood disorders. The key diagnostic criterion for major depressive disorder is the presence of a major depressive episode.
“There are nine symptoms that define a major depressive episode. Of the nine, at least five must have been present during a 2-week period. They must represent a change from previous functioning and they must cause significant impairment in daily functioning. At least one of the five symptoms must be either the first or the second symptom in the following list:
“1. Depressed mood most of the day, nearly every day.
“2. Reduced interest or pleasure in all or almost all activities.
“3. Significant weight loss or weight gain, or a significant decrease or increase in appetite.
“4. Trouble sleeping or sleeping too much.
“5. Psychomotor agitation or retardation.
“6. Fatigue or loss of energy.
“7. Feeling worthless or guilty in an excessive or inappropriate manner.
“8. Problems in thinking, concentrating, or making decisions.
“9. Recurrent thoughts of death, suicidal ideation, specific suicidal plan, or a suicide attempt.” (1 Encyclopedia of Mental Health (Academic Press 1998) pp. 735-736.)
“External stressors and significant life changes, such as chronic medical problems, death of a loved one, divorce or estrangement, miscarriage, or loss of a job, also can result in a form of depression known as adjustment disorder. Although periods of adjustment disorder usually resolve themselves, occasionally they may evolve into a major depressive disorder.” (Health & Wellness Resource Center, at http://infotrac.galegroup.com [as of June 23, 2005].)