A Horse Vet Blew a 0.087 on a Breathalyzer Without Drinking: Here’s What That Means for Your DWI Case

A peer-reviewed study published in Veterinary Sciences examined what happens when equine veterinarians perform abdominal ultrasounds on horses using ethanol as a coupling agent which is a standard, routine procedure in equine medicine. The veterinarians did not drink any alcohol. They poured or sprayed ethanol solution onto the horse’s skin to create contact between the ultrasound probe and the body, the same way they do it every day in every equine practice in the world.

Then they blew into an evidential-grade infrared breath alcohol analyzer which is the same type of instrument used by law enforcement to arrest people for DWI.

The results should concern anyone who has ever been asked to provide a breath sample during a traffic stop.

The Numbers

The study enrolled six veterinary students who each performed six ultrasound examinations on a horse, for a total of 36 sessions. Immediately after each procedure, the operator blew into a Dräger Alcotest 7110 which is a widely used evidential breathalyzer approved in both Europe and Australia.

83% of the time, the breath test was positive. Every single participant tested positive in at least four of their six sessions without consuming any alcohol.

The highest reading recorded was 0.087% which is above the legal limit in every state in the United States. That reading came from a person who had not had a drink in at least 24 hours. They were sober. They had been examining a horse.

Among the key findings:

• 30% of the readings at time zero were above 0.050%, which is the per se limit in many countries, in Utah, and for a commercial driver in Texas, where the threshold is 0.04
• 53% were in the “positive but below the legal limit” range (0.019%–0.050%)
• Positive results persisted for up to 60 minutes after the procedure ended
• When more than 1 liter of ethanol was used (common in extended colic exams), 100% of participants tested positive, with a median reading of 0.023% still registering at 30 minutes post-procedure
• Results above the legal driving limit persisted for up to 35 minutes in some cases

The study’s authors concluded that equine veterinarians who attend colic emergencies (which can happen at any hour of the day or night) can test positive on a breath alcohol test for up to an hour after the procedure, and recommended waiting at least 35 minutes before driving.

How Does This Happen?

The veterinarians were not drinking. They were not absorbing alcohol through their skin because they wore nitrile gloves throughout the procedures. They were inhaling ethanol vapor while working in close proximity to a large surface area saturated with 90% ethanol solution.

Breath alcohol testing assumes the alcohol it detects came from your blood, crossed into the lungs, and was exhaled in a fixed proportion to your blood alcohol concentration. When alcohol reaches the breath by some other route, the instrument cannot tell, and nothing on the printout reveals it. The most familiar version of that problem is mouth alcohol, and the 15-minute observation period built to guard against it is covered on Mouth Alcohol and the Breath Test.

What matters here is the exposure route this study documented, which is not a mouthful of anything. It is ambient vapor. Prior research had put the duration of that effect at 5 to 10 minutes for hand sanitizer and alcohol-based mouthwash. The equine study found something considerably longer.

There is a second possibility the authors raise, and it is stranger than contamination. They suspect at least some of the readings reflected actual pulmonary absorption, meaning the ethanol crossed into the bloodstream through the lungs rather than sitting in the airway. If that is right, those veterinarians did not merely appear to have alcohol in their blood. They briefly did, without drinking anything.

Why This Matters for DWI Defense

Nobody is going to get arrested for performing an ultrasound on a horse. But the science in this study has direct implications for DWI defense, because the route it documents is one the instrument and the protocol were never built to catch. This is not mouth alcohol. Nothing was in these subjects’ mouths. Ethanol in the surrounding air reached the breath sample by inhalation, and possibly crossed into the blood through the lungs, and neither the observation period nor the slope detector is designed to find either one.

Fifteen Minutes Was Not Enough

The entire premise of the 15-minute observation period is that residual alcohol dissipates inside that window. Veterinarians in this study who used more than a liter of ethanol were still testing positive at 30 minutes. Some were still positive at 60.

That is the finding with teeth in it. If environmental ethanol can defeat the observation period under controlled conditions, the question in a real case is not only whether the officer ran the clock honestly. It is whether 15 minutes was ever long enough given what that particular person had been breathing before the stop.

The instrument offers no help with that question. The Dräger Alcotest 7110 used in the study is evidential-grade, with both electrochemical and infrared sensors, and it still could not separate inhaled ethanol from ethanol that crossed the alveolar membrane. The Intoxilyzer 9000 Texas uses has the same limitation, and it does not flag it either.

Who Else Breathes Ethanol All Day

The horse is memorable but incidental. The same exposure route runs through healthcare workers using alcohol hand rub dozens of times a shift, brewery and distillery workers, and anyone working around ethanol-based solvents and cleaning agents. Exposure to non-ethanol chemicals causes a related but separate problem, and those are covered on Medical Conditions That Cause False Breath Tests.

The equine study adds to a growing body of forensic science literature demonstrating that breath alcohol testing is not the simple, infallible measurement that prosecutors present it to be. The instrument produces a number. The question is whether that number accurately reflects the defendant’s blood alcohol concentration at the time of driving and the answer depends on factors that the instrument itself cannot evaluate.

The Defense Takeaway

A breath test result is a number produced by a machine that assumes it knows where the alcohol came from. This study is an unusually clean demonstration of what happens when that assumption is wrong: six sober people, controlled conditions, an evidential-grade instrument, and results that would have put every one of them over the legal limit. No drinking. No impairment. Just ethanol vapor and a machine that cannot tell where the alcohol came from.

The full set of questions a breath result has to survive is on How Accurate Is the Breathalyzer in Texas. This page exists to establish one of them, and to establish it with data rather than argument: ethanol in the air around you can put a number on the printout.

Deandra Grant’s Master’s Degree in Pharmaceutical Science, ACS-CHAL Forensic Lawyer-Scientist designation, and training at Axion Analytical Labs give her the scientific credentials to challenge breath test results at the scientific level — not just the number on the printout, but the science behind how that number was generated and whether it can be trusted. When a breath test result is the centerpiece of a DWI prosecution, the defense must be equipped to ask the questions the instrument cannot answer.

If you have been arrested for DWI in Texas based on a breath test result, call (214) 225-7117 or visit texasdwisite.com. The number on the printout may not be what the prosecution says it is.