State v. Mayo, 465 P.3d 267

Police stopped a car after a traffic infraction; a K‑9 alerted and officers searched the vehicle. A plastic bag with a usable quantity of methamphetamine was found in the front pocket of a backpack on the passenger‑side floorboard. Defendant was charged with unlawful possession of methamphetamine (ORS 475.894).
Defendant testified at trial that the backpack was his but that he had left it earlier in a friend (Gillenwater)’s car, that he did not know drugs were in it, and that he only learned of the drugs when an officer removed them; he called no corroborating witnesses (Gillenwater or Claros).
During the state’s rebuttal closing, the prosecutor argued that it was unlikely someone would plant drugs in the backpack and commented on defendant’s failure to call witnesses to corroborate his story; defense counsel objected and the trial court overruled the objection.
Jury convicted defendant of unlawful possession; defendant appealed, arguing the prosecutor’s comments impermissibly shifted the burden of proof by suggesting he was required to call witnesses to prove his lack of knowledge.
The Oregon Court of Appeals held the prosecutor’s comments were improper because lack of knowledge is an element (mental state) the State must prove, not an affirmative defense the defendant must establish; the error was not harmless and the conviction was reversed and remanded.

Issue	Plaintiff's Argument	Defendant's Argument	Held
Whether prosecutor may comment on defendant’s failure to call witnesses re: his claimed lack of knowledge (burden shift)	Prosecutor may comment on deficiencies in defense evidence when defendant raises matters that impose a burden of production (e.g., by testifying to a version of events)	Comments impermissibly shifted burden; knowledge is an element the State must prove and defendant bore no burden to call corroborating witnesses	Reversed: prosecutor’s comments created a realistic possibility of confusing jurors about the burden of proof and were improper because defendant did not raise an affirmative defense or assume a production burden
Whether the error was harmless	Trial court’s instructions that the State bears the burden of proof and generic credibility instructions cured any error	Error prejudiced defendant because credibility of his testimony was central, the court’s overruling reinforced the prosecutor’s comment, and the verdict was nonunanimous	Not harmless: prejudice likely affected verdict; reversal and remand required

State v. Totland, 296 Or. App. 527 (prosecutor must not argue in a way that realistically confuses jurors about the ultimate burden of proof)
State v. Spieler, 269 Or. App. 623 (limited circumstances when prosecutor may comment on defendant’s failure to present evidence)
State v. Rainey, 298 Or. 459 (reversible error where allocation of burden on an element shifted to defendant)
State v. Harper, 296 Or. App. 125 (knowledge is a culpable mental state that the State must prove for possession offenses)
State v. Worth, 231 Or. App. 69 (overruling an objection can lead jurors to treat prosecutor’s remark as a correct statement of law)