The California Supreme Court unanimously ruled on July 18, 2002 in the case of Myron Mower that medical marijuana patients should be protected from unnecessary prosecution, declaring, "Possession and cultivation of marijuana is no more criminal - so long as its conditions are satisfied - than the possession and acquisition of any prescription drug with a doctor’s prescription."  Chief Justice Ronald M. George wrote that California's Proposition 215 law "reasonably must be interpreted to grant a defendant a limited immunity from prosecution."

On December 16, 1997, defendant Myron Carlyle Mower was charged with possession and cultivation of marijuana.  The charges arose from a July 11, 1997 search of his residence (while Mower was hospitalized due to complications from diabetes) during which the Tuolumne County Sheriff's Department discovered a 31-plant marijuana garden.  Myron Mower pleaded not guilty at arraignment and testified at his trial.  He was convicted by the jury; the verdict was first affirmed by an appeals court before the State Supreme Court returned the case to the appeals court for a new trial.

Myron Mower's charges were dropped by the Tuolumne County D.A. The Supreme Court has established a two-step process for patients who are arrested. First, a pretrial hearing is held, where the case can be dismissed if the defendant shows a preponderance of evidence regarding legal patient status.  Second, if a defendant is brought to trial, he or she need only raise a reasonable doubt as to innocence.  The new standard of evidence is that defendants must be found guilty "beyond a reasonable doubt" not merely by "preponderance of evidence," a weaker standard that had previously been used by the courts.

Sources (incomplete):

Gieringer, Dale. "State Supreme Court Mower Ruling Protects Prop. 215 Patients." CA NORML News. California National Organization for the Reform of Marijuana Laws, 18 July 2002. Web. 22 Feb. 2013. <http://www.canorml.org/news/mowerdecision.html>.