A state may establish that it is no longer a state-level crime for patients to possess or cultivate marijuana for medicinal purposes. Most exemptions are tied to a state registry program, which allows patients' credentials to be easily verified. With a simple defense to a charge of marijuana cultivation or possession, the defendant need only produce a relatively small amount of evidence at trial in support of the defense that the cultivation or possession was solely for a legitimate medical purpose. In order to win a conviction, the state must disprove the existence of facts establishing the defense beyond a reasonable doubt.
Maine is the only state where unregistered patients are afforded a simple defense at trial.
In contrast to the affirmative defense, which places the burden on defendants to prove that their marijuana use or possession is medically necessary, a simple defense places the burden on prosecutors to prove that marijuana use or possession is not medically necessary for the defendant. As a result, it is difficult for prosecutors to win a conviction against legitimate patients afforded a simple defense in medical marijuana cases. Several state medical marijuana laws allow individuals to assert an affirmative defense to charges of unlawful marijuana cultivation or possession. The affirmative defense is the only defense afforded individuals by the medical marijuana law in Alaska. Although this defense does not prevent patients from being arrested, as a matter of practice, individuals who are clearly in compliance with the law are typically not arrested.