People v. Lawson, 215 Cal. App. 4th 108

Defendant Brent Kerrigan Lawson was convicted of petty theft for stealing a $20 hoodie from Walmart; he had three prior theft/burglary priors and a prison-prior enhancement under § 667.5.
On appeal, Lawson contends the trial court erred by not giving a sua sponte instruction on mistake of fact, arguing he may have forgotten the hoodie and did not intend to steal it.
The appellate court agrees the evidence could support a forgetting theory, but holds it does not support a mistake-of-fact instruction as a matter of law.
The court explains mistake of fact negates mens rea only in limited circumstances where a mistaken belief would render the act innocent; forgetting the hoodie does not meet that standard.
Even if substantial evidence supported such an instruction, the court held there is no sua sponte duty to instruct on mistake of fact or similar defenses that only negate the mental state.
The judgment was affirmed, and the opinion clarifies that the jury was correctly instructed on the mental state element via CALCRIM No. 1800.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Duty to instruct on mistake of fact sua sponte	Lawson contends the court must instruct on mistake of fact sua sponte.	People argue no duty to sua sponte give such a defense when it negates only the mental state.	No sua sponte duty; mistake of fact not applicable.
Mistake of fact applicable to forgetting hoodie	Forgetfulness could negate intent to steal.	Forgetting the hoodie does not reflect a belief making the act innocent.	Mistake of fact inapplicable; no innocent act under these facts.
Impact of Anderson on instructional duties	Even with substantial evidence, duty may arise.	Anderson limits sua sponte duties to defenses that negate the mental state, not mere theories.	Anderson controls; no sua sponte duty to instruct on mistake of fact.

People v. Russell, 144 Cal.App.4th 1415 (Cal. Ct. App. 2006) (mistake-of-fact requires actual belief that would render act innocent; distinguishable here)
People v. Osborne, 77 Cal.App.3d 472 (Cal. Ct. App. 1978) (mistake-of-fact defense does not render conduct lawful)
Anderson v. Superior Court, 51 Cal.4th 989 (Cal. 2011) (no sua sponte duty to instruct on accident/mistake defenses that negate only mental state; pinpoint instruction upon request)
People v. Saille, 54 Cal.3d 1103 (Cal. 1991) (defense instructions require request for pinpoint instructions when negating elements)
People v. Jennings, 50 Cal.4th 616 (Cal. 2010) (general principles of law and mentals state instructions)