The prescription drug defense comes from Iowa law in Iowa Code Chapter 321J. “[The section criminalizing OWI] does not apply to a person operating a motor vehicle while under the influence of a drug if the substance was prescribed for the person and was taken under the prescription and in accordance with the directions of a medical practitioner as defined in chapter 155A or if the substance was dispensed by a pharmacist without a prescription pursuant to the rules of the board of pharmacy, if there is no evidence of the consumption of alcohol and the medical practitioner or pharmacist had not directed the person to refrain from operating a motor vehicle. When charged . . . a person may assert, as an affirmative defense, that the controlled substance present in the person's blood or urine was prescribed or dispensed for the person and was taken in accordance with the directions of a practitioner and the labeling directions of the pharmacy, as that person and place of business are defined in [the section governing the certification and operation of pharmacies in Iowa].”

A prescription drug defense is never allowed if there is evidence of alcohol, however. “Once a defendant has presented evidence sufficient to show the prescription drug defense applies, the State has the burden of disproving each element of the defense beyond a reasonable doubt.” State v. Schories, 827 N.W.2d 659, 665 (Iowa 2013). Once the Defendant presents evidence he or she has been taking medication pursuant to a valid prescription, the State must prove beyond a reasonable doubt that there substantial evidence to support the jury's conclusion that the defendant at the time of his arrest was not taking the prescribed medication according to his physician's instructions and the labeling directions of the pharmacy. Id. Something very important to note here. The defendant’s consumption of alcohol—any alcohol—voids the defense. Moreover, even if the defendant has a prescription for a particular medication, he or she cannot misuse it against doctors’ orders. The mere presence of a particular drug, other than marijuana metabolites, does not prove misuse. But one more thing is very important here—the patient/defendant must follow the doctor’s orders. If the doctor orders that the Defendant not operate machinery and the Defendant goes out and drives, the Defendant is misusing the drug. If the patient self-prescribes changes in levels or otherewise fails to follow doctor’s orders specifically—and the prosecutor can present evidence that is the case, a jury may conclude the defense does not apply. ​A blog is not legal advice. No attorney-client relationship is established by reading a blog or sending unsolicited information to an attorney over the Internet.