In the prosecution of marijuana for sale where the defendant asserts a defense under the Compassionate Use Act, an officer who has no experience in distinguishing patterns of lawful from unlawful possession is not qualified to testify as an expert. (People v. Hunt (1971) 4 Cal.3d 231.) In a prosecution for possession of marijuana for sale, defense evidence was presented that appellant had been prescribed marijuana for treatment of pain and depression. The prosecutions sole witness, a sheriffs officer, testified as a percipient witness and gave his opinion as an expert witness. Because the record failed to show that he was familiar with patterns of lawful possession for medicinal use that would allow him to differentiate from unlawful possession for sale, he was unqualified to testify as an expert and the evidence was insufficient to support a conviction.