Washington State Prescription and Drug DUI Defense

Vancouver, Clark, Skamania, Cowlitz, Thurston, Mason, Jefferson and Pacific Counties in Washington State— Defending DUI charges involving prescription drugs, marijuana, and other substances

Many people in Washington are arrested for driving under the influence of prescription medications such as Ambien, oxycodone, OxyContin, Wellbutrin, and Zoloft, or substances such as marijuana. Sometimes blood tests reveal a combination of prescription medications, alcohol, and other substances. In other cases, the only substance identified is a medication that the person was legally prescribed and taking for a legitimate medical condition.

The presence of a drug in someone’s bloodstream does not necessarily establish that the person was impaired by it. Yet these cases can result in serious criminal charges, loss of driving privileges, and consequences for employment and professional licensing.

Prescription Medications, Impairment, and the Limits of Toxicology

Not every medication affects driving in the same way. Some prescription drugs can substantially impair a person’s ability to drive, while others may have little or no appreciable effect at a particular dosage or under particular circumstances. The effects may depend on the medication, the amount consumed, the timing of administration, interactions with other substances, and individual physiology.

Stress, exhaustion, distraction, medical conditions, and other ordinary human experiences can also affect driving or produce symptoms that police mistakenly attribute to drug impairment.

The prosecution may rely on toxicologists or other expert witnesses to interpret blood-test results and offer opinions about impairment. But expert testimony is not beyond challenge simply because the witness works for the government. Scientific conclusions depend on the quality of the underlying research, the validity of the methods employed, and whether those conclusions actually apply to the individual accused.

What Washington Law Requires in Drug DUI Cases

Under RCW 46.61.502, Washington establishes specific statutory thresholds for alcohol and THC: an alcohol concentration of 0.08 or greater, or a THC concentration of at least 5.00 nanograms per milliliter of whole blood, within two hours after driving. The State may also prosecute cases involving alcohol, cannabis, or other drugs based on evidence that the driver was under the influence of or affected by those substances, even without proof of those numerical thresholds.

Unlike alcohol and THC, Washington law does not establish a specific blood-concentration limit for most other drugs. Instead, the prosecution must establish impairment under the applicable statutory standard. Having a lawful prescription is not, by itself, a defense, but neither does a positive toxicology result automatically resolve whether a person’s driving was affected by the substance detected.

These distinctions raise difficult scientific, evidentiary, and sometimes constitutional questions. They require careful analysis rather than simply accepting an officer’s observations or a laboratory scientist’s interpretation.

Challenging the Science and the Government’s Evidence

At the Dalton Law Office, we carefully scrutinize drug DUI investigations, blood-testing procedures, toxicology reports, and the scientific foundations of expert opinions. We examine whether the substances detected could have caused the impairment alleged, whether the government’s interpretations are supported by reliable science, and whether other explanations for the observed behavior have been adequately considered.

We are prepared to litigate these issues through pretrial motions, evidentiary hearings, expert testimony, and trial when necessary. Depending on the case, that litigation may involve the admissibility of scientific evidence, the scope and foundation of expert opinions, the instructions presented to the jury, or constitutional challenges supported by the facts and law.

We do not believe that a laboratory report should substitute for proof, or that a government expert’s opinion should go unquestioned. These cases deserve a defense that understands the science, challenges unsupported assumptions, and holds the State to its burden of proof.

Get Experienced Help With a Drug DUI Charge

If you are facing DUI charges involving prescription medications, marijuana, or other drugs, call 360-213-0013 to speak with Ms. Dalton or another attorney at the Dalton Law Office, PLLC, or to schedule a consultation.

We make ourselves personally available as soon as possible for DUI and related charges. For emergencies outside regular business hours, call our office for the after-hours contact information provided in our recorded message.