Medical Conditions That Mimic Intoxication

Why the Signs Overlap

An officer at the roadside is not diagnosing you. He is reading indicators off a list, and the list was built to detect one thing.

Bloodshot eyes. Slurred speech. Poor balance. Confusion. Slow responses. Jerking eye movement. Every item is a symptom, and symptoms are not specific to their cause. The same presentation that reads as intoxication reads to a physician as a metabolic problem, a neurological problem, an inner ear problem, or an injury.

The officer’s own training acknowledges this, which is the part worth knowing. Before the eye test, he is trained to screen for medical causes: check that the pupils are equal in size, check for nystagmus while the eyes look straight ahead, and check that both eyes track together. If the pupils differ distinctly in size, the training tells him the subject may have a prosthetic eye, a head injury, or a neurological disorder. If the eyes do not track together, it tells him a serious medical condition or injury may be present. He is also instructed to ask whether the subject has suffered any head injuries.

So the question is rarely whether medical conditions can cause these signs. The officer was trained that they can. The question is whether he performed the screening, what he asked, and what he wrote down.

None of the conditions below automatically invalidate a test result or a charge. What they do is raise documented questions about whether what the officer observed, or what the instrument reported, means what the State says it means.

Diabetes

Diabetes affects a DWI case two separate ways, and they get confused with each other constantly.

The behavioral route. Low blood sugar and diabetic ketoacidosis can produce confusion, disorientation, slurred speech, unsteadiness, and poor coordination. A driver in a metabolic crisis and a driver who has been drinking can look very similar at the roadside. Ketoacidosis can develop rapidly, and someone experiencing it needs a hospital, not a jail cell.

The chemical route. When the body cannot properly metabolize glucose, it turns to fat for energy. The byproducts include ketone bodies, one of which is acetone, and acetone is exhaled through the lungs. The Intoxilyzer 9000 identifies compounds by how they absorb infrared light at specific wavelengths, and acetone absorbs at wavelengths that partially overlap with ethyl alcohol. Depending on the concentration and the detection channels used, that can inflate the reported result.

The instrument includes an interferent detection system meant to flag non-ethanol compounds. It is not a complete safeguard, and a result that was not flagged is not proof that no interferent was present.

More on the instrument itself is on Intoxilyzer 9000 Problems.

The Ketogenic Diet

You do not need to be diabetic to be in ketosis. The metabolic state that produces acetone in the breath is triggered any time the body shifts from glucose to fat metabolism, including in otherwise healthy people following ketogenic or very low-carbohydrate diets.

That matters because the diet is common now. Someone eating strictly low-carbohydrate for weeks or months may have chronic low-level ketosis with measurable acetone in their breath at baseline, entirely unrelated to alcohol. If that person then has a drink or two, the actual alcohol and the acetone-related interference can combine into a result that overstates the alcohol component.

This is not a hypothetical edge case. It is documented in the forensic toxicology literature, and it is relevant in any case where dietary habits can be established through records or personal history.

Acid Reflux and GERD

Reflux moves stomach contents, including any alcohol still in the stomach, back up into the esophagus and mouth. A breath instrument is designed to sample deep lung air, which reflects blood alcohol concentration. It has no reliable way to distinguish alveolar air from alcohol vapor that originated in the stomach. The result is a reading higher than the person’s actual blood alcohol concentration, and the reflux event can be silent, meaning the person feels nothing and the officer sees nothing during the observation period.

That mechanism, the fifteen minute observation period that is supposed to catch it, and the research on how well it works, all belong to Mouth Alcohol and the Breath Test.

Auto-Brewery Syndrome

This one has to be described precisely, because overstating it damages the credibility of everything else on this page.

Auto-brewery syndrome, also called gut fermentation syndrome, is a rarely diagnosed condition in which microorganisms in the gastrointestinal tract ferment dietary carbohydrates into ethanol inside the body. The mechanism is generally understood as an overgrowth of yeast or certain bacteria, often following heavy antibiotic use, a high-carbohydrate diet, or gastrointestinal disease. Because the alcohol is produced internally, a person can register above the legal driving limit without having consumed anything.

Contributing factors identified in the literature include carbohydrate-rich diets, gastrointestinal surgery, Crohn’s disease, obesity, diabetes, gastroparesis, liver dysfunction, antibiotics, and a compromised immune system. It has been documented in men, women, and children, and can occur in otherwise healthy individuals.

Now the honest part. It is rare, it is almost certainly underdiagnosed, and asserting it is worthless without proof. Establishing it requires a clinician familiar with the condition and a controlled carbohydrate challenge test, where the patient consumes a high-carbohydrate meal or glucose solution in a monitored setting and blood alcohol is measured over several hours, plus testing for ethanol-producing organisms. Courts rejected this defense for decades. It has succeeded in a small number of cases, and in every one the difference was laboratory confirmation, not assertion. The full history of the condition, who it affects, and what a lab-confirmed defense actually requires is covered in Auto-Brewery Syndrome: When Your Body Brews Its Own Alcohol.

Head Injury

The fact pattern that matters most here is the one people miss: the injury sustained in the crash that brought the police.

A driver in a collision can suffer a concussion or worse and then be evaluated for DWI minutes later by an officer who has no idea. Head injury can produce confusion, disorientation, slurred or slowed speech, memory gaps, unsteadiness, unequal pupils, and abnormal eye movement. Every one of those is on the officer’s indicator list.

His training tells him unequal pupil size may indicate a head injury, and instructs him to ask about head injuries during the eye-test prescreening. Whether he did is a discoverable fact. So is whether anyone offered medical attention, what the paramedics documented, and whether an emergency room saw the same person hours later and reached a different conclusion.

Inner Ear and Balance Disorders

The one-leg stand and the walk-and-turn assume a body that a great many people do not have.

The original validation research behind these tests suggested that people over 65, people with back, leg, or inner ear problems, and people who are overweight by 50 or more pounds may have difficulty performing them. That is not a defense lawyer’s characterization. It is in the officer’s own training material, which also notes that fewer than 1.5% of the subjects in the original studies were over 65 and that the final report included no data on subject weight at all.

So when a 58-year-old with a bad knee and a vestibular disorder cannot hold a foot six inches off the ground for thirty seconds on the shoulder of a highway, the test has not measured intoxication. It has measured a bad knee and a vestibular disorder. See Who Fails Field Sobriety Tests While Sober.

What Else Causes Nystagmus

Nystagmus is involuntary jerking of the eye, and alcohol is one cause among many. The officer’s training manual describes multiple types, including vestibular and neural nystagmus, and acknowledges that pathological conditions such as brain tumors, brain damage, and diseases of the inner ear may produce the same horizontal jerking the officer is scoring. The training covers that entire medical subject in a few pages. Environmental conditions matter too: wind and dust irritating the eyes, and visual distractions from rotating lights, strobes, or passing traffic, were listed in an earlier version of the training as interfering with the test.

The whole eye test, how it is supposed to be administered, and how it fails is on HGN Eye Test.

Prescription Medication

Be careful with this one, because the intuitive answer is wrong.

A lawfully prescribed medication is not a defense to impairment in Texas. The intoxication definition reaches a controlled substance, a drug, a dangerous drug, or any other substance introduced into the body, and it does not care whether a physician authorized it. If a prescription drug caused you to lose the normal use of your mental or physical faculties, the DWI statute applies.

What medication history contributes is real but different. Some medications contain ethyl alcohol as a solvent, which is a mouth alcohol problem. Some matter because tolerance means a stable therapeutic concentration says little about your functioning. And some simply explain a sign the officer attributed to alcohol, since many affect pupil size. The full treatment is on Drug DWI in Texas.

When Occupational Exposure Does It

There is one more category, and it is the strangest evidence in this area.

A peer-reviewed study examined equine veterinarians performing routine abdominal ultrasounds on horses, a procedure that uses ethanol as a coupling agent. The veterinarians drank nothing. They wore gloves. They breathed the vapor. Then they blew into an evidential-grade breath alcohol instrument, and a substantial share of the readings came back positive, with the highest above the legal limit in every American state.

The mechanism generalizes. Compounds documented as potential interferents on infrared instruments include toluene, xylene, acetone, methyl ethyl ketone, isopropanol, and various solvents. People in painting, auto body repair, construction, manufacturing, chemical processing, dry cleaning, or laboratory work can be exposed to them, and someone tested shortly after leaving work may carry residual compounds the instrument cannot distinguish from ethyl alcohol.

The full study is covered separately: A Horse Vet Blew a 0.087 on a Breathalyzer Without Drinking.

What Documenting a Condition Actually Requires

Here is the thing that decides whether any of this helps you: a condition you assert is worth nothing, and a condition you document can be worth the case.

What that takes:

• Records that predate the arrest. A diagnosis made after you were charged invites the argument that it was manufactured for the case. A condition in your chart from three years ago does not.
• A treating physician who has managed the condition, can describe how it presents in you specifically, and can testify.
• Timing. It is not enough that you have GERD. The question is whether you were symptomatic that night. Refill dates, glucose logs, and appointment records around the arrest date speak to that.
• The arrest record. Body camera and dash camera footage, the offense report, jail medical intake, and any emergency room visit. Whether you told the officer, and what he did with it, is on the video.
• The instrument or laboratory file where the condition affects the test rather than your behavior.

Preserving what only you know is on What You Can Do to Help Your Own Case.

Turning It Into a Ruling or a Defense

A medical condition becomes a legal argument in one of two places.

Sometimes it becomes a challenge to the reliability of the State’s scientific evidence, litigated in a hearing before the jury hears the number. That is the stronger route when the condition affects the test rather than your behavior. See Challenging Expert Testimony and the Kelly Hearing.

More often it becomes a jury argument, presented through medical records and a physician, that the State’s evidence has an alternative explanation it never ruled out. Neither outcome is certain, and the difference between a medical defense that works and one that embarrasses everyone is documentation. See What Are the Most Common DWI Defenses in Texas?.

Go deeper on the breath-test side of this page: Medical and Physiological Conditions That Can Produce a False Breath Test Result*.