Intent May Be Proven Circumstantially
It is well established that intent may be proven circumstantially. (1 Witkin, Cal. Evidence (3d ed. 1986) Circumstantial Evidence, 408, pp. 381-382.)
In People v. Garcia (2001) 25 Cal.4th 744, the Supreme Court recognized that " although notice alone does not satisfy the willfulness requirement, a jury may infer from proof of notice that the defendant did have actual knowledge, which would satisfy the requirement." ( 25 Cal.4th at p. 752.)
The court acknowledged that in some cases potential difficulties of proof have justified interpreting statutes to include criminal negligence, i.e., conviction based on what the defendant reasonably should have known, but it pointed out that these cases generally involve affirmative acts, and should not be applied to the registration statute which involves only the failure to act. (Ibid.)
While it may be an easy matter for a defendant to say that he forgot, it is another matter to convince a jury that this is true.
Grumet v. State (Fla.Ct.App. 2000) 771 So. 2d 39 at page 43 illustrates that the trier of fact may well reject a defendants "testimony that he forgot all about it." The same has proven true in perjury prosecutions. (E.g., People v. Tolmachoff (1943) 58 Cal. App. 2d 815, 821 evidence sufficient to support jurys finding of willfulness, rejecting defendants testimony that her prior statements reflected "her best recollection, honestly given, as to what occurred nearly a year prior to the time she testified'; People v. Todd (1935) 9 Cal. App. 2d 237, "The question of whether the false swearing is the result of an honest mistake or has been committed willfully, knowingly and corruptly is one of fact for the jury to decide , and evidently the jury in the present case, as shown by its verdict, did not believe the story told by appellant.".)