Quick answer: In Arizona you may be able to prove the affirmative defense to a Prescription Drug DUI using pharmacy prescription records alone — admitted under the business records exception to the hearsay rule — without ever putting a doctor, pharmacist, or other witness on the stand.
What Is a Prescription Drug DUI in Arizona?
Under Arizona law, a person is guilty of a Prescription Drug DUI if a prescription drug impairs them to the slightest degree while driving, and that drug is found in their blood. Arizona’s DUI statutes are written broadly: the State does not need to prove a driver was using the drug improperly, only that they were impaired and that the drug was present in their system.
However, Arizona law also provides a critical protection for people who are legitimately following their doctor’s instructions. If the prescription drug was taken exactly as prescribed by a licensed medical professional, the law allows the defendant to raise an affirmative defense that can lead to a not-guilty result, even if the drug was present in their blood and contributed to impairment.
What Is an Affirmative Defense, and Who Has to Prove It?
An affirmative defense is different from simply denying the charge. Once the State proves its case, the burden shifts to the defendant to prove the affirmative defense by a preponderance of the evidence — meaning it is more likely than not that the statement is true. This is a much lower bar than the State’s burden of proving guilt beyond a reasonable doubt, but it is still a burden the defense must meet with actual evidence.
How the State Builds Its Case First
Before the defense burden ever comes into play, the State must present evidence that an active prescription drug was present in the blood sample taken by police. This evidence typically comes from the testimony of the crime lab analyst, often called a criminalist, who performed the blood testing. Lab results in Arizona DUI cases almost always report the specific quantity of the active drug detected, and the criminalist is generally well-versed in how that drug affects the body.
Only after the State has presented this evidence does the burden shift to the defendant to show the drug was taken as prescribed.
Two Ways to Prove the Drug Was Taken as Prescribed
Option 1: Testimony From the Prescribing Medical Professional
The most direct way to prove the affirmative defense is to have the prescribing doctor or medical professional testify that they prescribed the drug, and that the level found in the defendant’s blood is consistent with taking it as directed. In practice, this option is often difficult to use. Many medical professionals are reluctant to appear in court, and scheduling a physician’s testimony can add significant delay and expense to a case.
Option 2: Pharmacy Prescription Records as a Hearsay Exception
A second, often more practical approach relies on Arizona’s Rules of Evidence rather than live testimony. Pharmacy prescription records contain most of what a defendant needs: by law, these records must identify the prescribing medical professional and include instructions on dosage and frequency.
Pharmacy records are technically hearsay — out-of-court statements offered to prove the truth of the matter asserted — and hearsay is normally inadmissible. However, pharmacy prescription records typically qualify for the business records exception to the hearsay rule, because they are created and maintained in the ordinary course of business by the pharmacy’s custodian of records.
Why courts treat pharmacy records as trustworthy: Pharmacies have a legal duty to keep accurate prescription records. Failing to do so can result in loss of the pharmacy’s license and even criminal liability. Because of this built-in accountability, courts have found pharmacy prescription records to be reliable enough to admit as an exception to the hearsay rule.
Step-by-Step: How a Defense Attorney Gets Pharmacy Records Into Evidence
- Issue a subpoena duces tecum. The defense attorney has the court issue a subpoena directing the pharmacy’s custodian of records to appear at trial with the prescription records.
- Authenticate without live testimony. In response, the custodian can sign a certificate confirming the records are authentic and send them directly to the court or the defense attorney — without ever appearing in court.
- Admit the records. The records become admissible as a hearsay exception unless the prosecutor can affirmatively show they are untrustworthy, which is rare given the pharmacy’s legal duty to maintain accurate records.
- Use the State’s own witness to confirm the defense. The defense attorney can ask the State’s criminalist whether, given the quantity of the drug found in the defendant’s blood, the defendant could have taken the drug as prescribed.
- Meet the burden of proof. If the criminalist agrees, the defendant has met the preponderance-of-the-evidence standard for the affirmative defense — using the prosecution’s own expert, and without calling a single defense witness.
What If the Criminalist Disagrees?
A defendant’s attorney does not have to find this out for the first time at trial. Arizona law gives defense attorneys the right to interview State witnesses, including the criminalist, before trial. If the criminalist’s answer would not support the defense, the attorney will typically know this in advance and can prepare to call an independent expert witness to testify that the dosage found is consistent with proper use of the prescription. While less efficient than relying on the State’s own witness, this backup approach still allows the defendant to meet the burden of proof.
Glossary: Key Legal Terms in This Defense
| Term | Meaning |
|---|---|
| Affirmative defense | A defense the defendant must prove, rather than simply denying the State’s allegations. |
| Preponderance of the evidence | The legal standard requiring the defendant to show something is “more likely than not” true. |
| Criminalist | A crime lab analyst who tests blood or other samples for the presence of drugs or alcohol. |
| Custodian of records | The person at a business, such as a pharmacy, legally responsible for maintaining its official records. |
| Subpoena duces tecum | A court order requiring a person to produce documents or records, rather than simply appear to testify. |
| Hearsay | An out-of-court statement offered to prove the truth of what it asserts; generally inadmissible unless an exception applies. |
| Business records exception | A hearsay exception allowing records kept in the regular course of business to be admitted into evidence. |
Frequently Asked Questions
Is it illegal to drive in Arizona with a prescription drug in your system?
Yes, but only under certain conditions. Arizona law makes it illegal to drive while impaired to the slightest degree by any drug, including a legally prescribed one, with that drug present in the blood. Simply having a prescribed medication in your system is not, by itself, a crime — impairment plus the presence of the drug is what the State must prove.
What is the affirmative defense to a Prescription Drug DUI in Arizona?
Arizona law allows a defendant to avoid conviction by proving, by a preponderance of the evidence, that the prescription drug found in their blood was taken exactly as prescribed by a licensed medical professional. The burden shifts to the defendant only after the State has presented evidence of impairment and the presence of the drug.
Do I have to put a doctor or pharmacist on the witness stand to win this defense?
Not necessarily. While testimony from the prescribing medical professional is one way to prove the defense, Arizona’s hearsay exception for business records allows pharmacy prescription records to be admitted into evidence without live witness testimony, often making it possible to establish the defense using documents alone.
What are pharmacy prescription records and why do they matter in a DUI case?
Pharmacy prescription records are business records a pharmacy is legally required to maintain, showing the prescribing medical professional and the exact dosage and frequency instructions for the medication. Because pharmacies must keep these records accurately or risk losing their license, courts generally treat them as trustworthy.
How does a defendant get pharmacy prescription records into evidence?
A defense attorney can have the court issue a subpoena duces tecum directing the pharmacy’s custodian of records to produce the records. The custodian can sign a certificate authenticating the records and send them to the court or defense attorney, allowing the records to be admitted without the custodian appearing in person, unless the prosecution shows the records are untrustworthy.
Can the State’s own crime lab analyst help prove the defense?
Often yes. The State’s criminalist who tested the blood sample can be asked, using the pharmacy records, whether the quantity of the drug found in the defendant’s blood is consistent with taking the medication as prescribed. If the criminalist agrees, the defendant can satisfy the burden of proof using the prosecution’s own witness.
What happens if the State’s criminalist disagrees that the dosage matches the prescription?
If the criminalist does not support the defense theory, the defendant’s attorney typically learns this in advance because Arizona law allows defense attorneys to interview State witnesses before trial. If the answer is unfavorable, the defense can call its own expert witness instead.
What is the legal standard of proof for this affirmative defense?
The defendant must prove the defense by a preponderance of the evidence, meaning it is more likely than not that the prescription drug was taken as directed by a medical professional. This is a lower standard than the State’s burden of proving guilt beyond a reasonable doubt.
Does this defense apply to all drugs found in a driver’s blood?
This affirmative defense applies specifically to drugs that were validly prescribed by a licensed medical professional and used according to that prescription. It does not apply to illegal drugs or to prescription medications used in a manner inconsistent with how they were prescribed.
About the Author: Gordon Thompson
Gordon Thompson has been a licensed Arizona attorney since 1982, with 47 years of total legal practice and more than 6,000 clients represented. He earned his law degree from Syracuse University College of Law, was admitted to the State Bar of New York in 1979, and is a member of the State Bar of Arizona. His practice is limited exclusively to DUI and criminal defense in Arizona, and he personally handles every aspect of each case — from the initial MVD hearing request through trial. Read Gordon’s full attorney profile.
This article is provided for general informational purposes only and does not constitute legal advice. Every DUI case depends on its specific facts, evidence, and procedural history. Reading this page does not create an attorney-client relationship. For advice about your specific situation, contact Gordon Thompson directly for a free consultation.