Mentch had a medical marijuana recommendation, 39 marijuana plants, a scale, baggies of marijuana, and other paraphernalia in his home when police officers searched it. His defense at his cultivation trial was that he regularly provided marijuana to five others who also had valid medical marijuana recommendations. He also counseled them on marijuana use and took them to their medical appointments. Following his conviction, he argued on appeal that the trial court improperly refused to give his requested “primary caregiver” instruction. The appellate court agreed and reversed the conviction. Under the Compassionate Use Act, a primary caregiver is the individual designated by the exempted person who has taken responsibility for the health and safety of that person. A defendant has a right to a jury instruction on an affirmative defense if there is substantial evidence. Here, Mentch presented sufficient substantial evidence to present the matter to the jury, and the trial court erred when it refused his instruction. The error was prejudicial, and therefore reversal was required.