Auto-Brewery Syndrome in Colorado DUI Cases
Most DUI cases involving alcohol begin with the assumption that the driver consumed beer, wine, liquor, or another alcoholic beverage before getting behind the wheel. In extremely rare cases, however, a person may produce alcohol inside their own body through a condition known as auto-brewery syndrome.
Auto-brewery syndrome, sometimes called gut fermentation syndrome, is a rare medical condition in which microorganisms in the gastrointestinal tract ferment carbohydrates and produce ethanol. A person experiencing an episode can potentially develop measurable alcohol levels and symptoms resembling intoxication even though they did not intentionally consume an alcoholic beverage. Current medical literature recognizes the condition, although diagnosis remains difficult and there are no universally standardized diagnostic criteria.
The condition can become particularly important when someone is arrested for DUI after insisting that they did not drink alcohol. A positive breath or blood test alone may not explain where the alcohol came from, but an auto-brewery defense requires substantially more than simply claiming that the body produced the alcohol.
Medical records, specialized testing, expert testimony, dietary history, microbiological evidence, and the circumstances surrounding the arrest may all become important when evaluating whether auto-brewery syndrome could realistically affect a Colorado DUI case.
Colorado Auto-Brewery Syndrome DUI Attorney
If you have been charged with DUI despite consuming little or no alcohol and you believe an undiagnosed medical condition may have contributed to the test results, the circumstances should be investigated carefully.
Colorado DUI defense attorney Matthew Martin at The Law Office of Matthew Martin can review the breath or blood testing, police reports, medical history, symptoms, laboratory records, and other evidence surrounding the arrest. When appropriate, the defense may also work with physicians, toxicologists, or other experts to determine whether auto-brewery syndrome or another medical condition could help explain an unexpected BAC result.
Call 303.725.0017 today to schedule a free consultation with The Law Office of Matthew Martin.
Overview of Auto-brewery Syndrome in DUI Cases in Colorado
- What Is Auto-Brewery Syndrome?
- How Can Auto-Brewery Syndrome Affect a Colorado DUI Case?
- Proving Auto-Brewery Syndrome After a DUI Arrest
- Blood and Breath Testing in an Auto-Brewery DUI Case
- Does Auto-Brewery Syndrome Cause High BAC Levels?
- Conditions Associated With Auto-Brewery Syndrome
- Can Auto-Brewery Syndrome Be Confused With Drinking?
- Expert Witnesses in Auto-Brewery DUI Cases
- Frequently Asked Questions
- Additional Resources
What Is Auto-Brewery Syndrome?
Auto-brewery syndrome occurs when microorganisms inside the body produce abnormal amounts of ethanol through fermentation. The condition most commonly involves the gastrointestinal system, where certain bacteria or fungi can ferment dietary carbohydrates into alcohol. Medical literature has associated the condition with organisms including certain species of Candida, Saccharomyces, Klebsiella, and E. coli, although the exact organisms and mechanisms can differ between patients.
Small amounts of endogenous alcohol can be produced during normal digestion, but those amounts ordinarily do not cause intoxication. Auto-brewery syndrome becomes clinically significant when alcohol production becomes high enough to produce measurable ethanol concentrations and symptoms.
Reported symptoms can resemble ordinary alcohol intoxication and may include impaired coordination, dizziness, slowed reactions, changes in speech, confusion, fatigue, mood changes, and difficulty concentrating. Symptoms may appear after eating carbohydrate-rich foods because those carbohydrates provide material that microorganisms can ferment into ethanol.
The condition appears to be rare. A 2025 review of published medical literature identified a relatively small number of documented patients and noted that delayed diagnosis is common. The rarity of the disorder is one reason courts and prosecutors may scrutinize an auto-brewery claim closely.
How Can Auto-Brewery Syndrome Affect a Colorado DUI Case?
Colorado recognizes several different alcohol-related driving offenses.
A person commits DUI by driving while alcohol or drugs affect the person to the point that they are substantially incapable of safely operating a vehicle. A person can be charged with DWAI when alcohol affects them even to the slightest degree so that they are less capable of safely driving than they ordinarily would be. Colorado also recognizes DUI per se, which generally applies when a person’s blood or breath alcohol concentration is 0.08 or higher at the time of driving or within two hours afterward. C.R.S. § 42-4-1301.
Auto-brewery syndrome can complicate that analysis because a driver may have measurable ethanol in the body without knowingly consuming alcoholic beverages.
In a traditional DUI case, prosecutors may attempt to establish alcohol consumption through evidence such as an admission to drinking, bar receipts, witness statements, alcoholic beverages found in the vehicle, field sobriety tests, and chemical testing. An individual with legitimate auto-brewery syndrome may instead have a positive chemical test while other evidence of conventional alcohol consumption is absent. That discrepancy can become important to the defense.
However, auto-brewery syndrome should not be viewed as an automatic DUI defense. Colorado’s DUI per se law focuses heavily on the driver’s BAC, and the impaired-driving statutes are strict-liability offenses. A medically verified explanation for the alcohol reading may still be highly relevant to the evidence, the source of the ethanol, the reliability of assumptions made during the investigation, and the prosecution’s theory of the case, but the legal significance will depend on the exact charge and facts.
Colorado law expressly permits a defendant charged with DUI per se to offer evidence showing a disparity between chemical-test results and other facts from which the judge or jury could infer that the test was defective or inaccurate. The statute specifically allows evidence concerning the absence of ordinary signs or symptoms of intoxication.
An auto-brewery case can therefore require both medical evidence and careful legal analysis, rather than relying solely on the existence of an unusual BAC result.
Proving Auto-Brewery Syndrome After a DUI Arrest
One of the biggest challenges in an auto-brewery DUI case is establishing that the condition actually exists.
There are currently no universally accepted standardized diagnostic criteria for auto-brewery syndrome. Modern medical guidance emphasizes that alcohol ingestion should first be considered and excluded because ordinary alcohol consumption is far more common than endogenous alcohol production. Objective evidence demonstrating alcohol production without outside alcohol consumption is therefore particularly important.
One diagnostic approach discussed in current medical literature is a supervised carbohydrate challenge test. The patient consumes a controlled carbohydrate load while being monitored, and alcohol levels are measured over time. The purpose is to determine whether the body produces ethanol despite the absence of external alcohol consumption. Current clinical guidance describes a monitored carbohydrate challenge as one of the preferred methods for objectively demonstrating endogenous ethanol production.
A medical evaluation may also include gastrointestinal testing and cultures intended to identify organisms capable of producing ethanol. Physicians may examine the patient’s medical history, diet, gastrointestinal conditions, antibiotic exposure, metabolic issues, and other factors that could contribute to abnormal microbial growth.
In a DUI case, potentially relevant evidence may include medical records documenting previous unexplained intoxication episodes, previous abnormal alcohol readings, statements from family members or coworkers who observed symptoms when the person had not been drinking, laboratory results, gastrointestinal testing, carbohydrate-challenge results, and testimony from treating physicians or medical experts.
Timing can matter considerably. A diagnosis first raised months after a DUI arrest may receive more scrutiny than a well-documented medical history showing unexplained intoxication episodes before the arrest. That does not necessarily mean a later diagnosis is invalid, but corroborating evidence becomes especially important.
Blood and Breath Testing in an Auto-Brewery DUI Case
Auto-brewery syndrome is not simply an allegation that a breath-testing machine falsely detected alcohol. The condition involves actual ethanol produced within the body, meaning both a breath test and a blood test could potentially detect alcohol during an episode.
That distinction separates an auto-brewery defense from conventional challenges involving equipment calibration, contaminated samples, improper blood storage, mouth alcohol, or testing procedures.
The defense may instead focus on why ethanol was present and whether the prosecution’s interpretation of the result accurately reflects what occurred.
A toxicologist may examine the measured BAC, timing of the test, expected alcohol absorption and elimination patterns, reported food intake, symptoms, and other evidence. Medical experts may separately address whether the person has a condition capable of generating endogenous alcohol.
Because auto-brewery syndrome can produce actual ethanol, the fact that a laboratory test was analytically accurate does not necessarily resolve the underlying medical issue.
At the same time, ordinary forensic defenses remain available when supported by the evidence. A DUI attorney may separately investigate whether the breath instrument was functioning properly, whether the blood sample was collected and stored correctly, whether fermentation or contamination occurred after collection, whether required testing procedures were followed, and whether the reported BAC accurately reflects the driver’s BAC at the relevant time.
Does Auto-Brewery Syndrome Cause High BAC Levels?
Published case reports have documented measurable and sometimes substantial ethanol concentrations in individuals diagnosed with auto-brewery syndrome. However, the amount of alcohol produced can vary significantly between people and between episodes.
For that reason, the existence of the syndrome does not establish that any particular BAC reading must have resulted from endogenous alcohol production.
A defense asserting auto-brewery syndrome must connect the diagnosed condition to the specific DUI incident.
Relevant questions may include what the person ate before driving, whether the person had symptoms associated with previous episodes, when those symptoms began, whether alcohol was available, what the breath or blood result showed, and whether medical testing can reproduce endogenous alcohol production under controlled conditions.
An expert may also need to explain whether the amount of alcohol allegedly produced by the person’s condition could reasonably account for the BAC reported in the DUI case.
Conditions Associated With Auto-Brewery Syndrome
Research suggests that auto-brewery syndrome is associated with disruption of the normal gastrointestinal microbiome. Potential contributing factors described in the medical literature include prior antibiotic exposure, diets high in refined carbohydrates and sugars, intestinal dysmotility, metabolic conditions, altered gastrointestinal anatomy, and microbial overgrowth.
The condition is not simply the result of eating bread or carbohydrates. Most people do not develop intoxicating amounts of ethanol after eating carbohydrate-rich foods.
Instead, auto-brewery syndrome involves an abnormal microbial environment that allows ethanol-producing organisms to generate unusually high amounts of alcohol.
Because other illnesses can produce symptoms resembling intoxication, physicians generally need to consider and exclude alternative explanations before diagnosing the condition.
Can Auto-Brewery Syndrome Be Confused With Drinking?
Yes. In fact, this is one of the central difficulties associated with diagnosing the disorder.
A person can smell or appear intoxicated, register alcohol on a breath or blood test, and display symptoms ordinarily associated with drinking. Family members, employers, physicians, police officers, and others may naturally assume that the person consumed alcohol.
Medical reviews have documented significant social and legal consequences arising from delayed or incorrect diagnosis, including alcohol-treatment referrals, employment problems, family conflict, and legal proceedings. Because ordinary alcohol consumption remains vastly more common, a court is unlikely to accept an auto-brewery explanation merely because the defendant denies drinking. Objective medical testing and corroboration can therefore be critical.
Expert Witnesses in Auto-Brewery DUI Cases
Expert testimony may be particularly important because auto-brewery syndrome involves medical and scientific issues that are outside ordinary experience.
A defense may involve a gastroenterologist or other physician who can explain the diagnosis, the patient’s medical history, gastrointestinal testing, and supervised carbohydrate-challenge results. A toxicologist may separately analyze the BAC evidence and explain whether the reported alcohol concentration is consistent with the proposed medical explanation.
Microbiology evidence may also become relevant when testing identifies ethanol-producing organisms in the digestive tract. The prosecution may challenge the diagnosis or present its own experts. Issues may include whether the testing was performed under controlled conditions, whether outside alcohol consumption was adequately excluded, whether the identified microorganisms actually produced enough ethanol to explain the DUI result, and whether the condition was active at the time of the arrest.
For this reason, an auto-brewery defense usually requires much stronger documentation than a defendant’s personal belief that the condition explains the BAC.
Frequently Asked Questions About Auto-Brewery Syndrome and DUI
Can auto-brewery syndrome cause a positive breathalyzer result?
Yes. Auto-brewery syndrome can cause the body to produce actual ethanol, which means alcohol may be detected on a breath test even when the person did not intentionally consume an alcoholic beverage. Because the alcohol is genuinely present in the body, a positive breath result is possible during an active episode.
Can auto-brewery syndrome also cause a positive blood alcohol test?
Yes. Unlike defenses involving mouth alcohol or a malfunctioning breath-testing device, auto-brewery syndrome involves alcohol that is produced internally and absorbed into the bloodstream. A properly performed blood test may therefore detect ethanol during an episode. The legal issue may become whether the medical condition can credibly explain the BAC result in the particular DUI case.
Is auto-brewery syndrome a complete defense to DUI in Colorado?
Not automatically. Colorado DUI law can focus on impairment and, in DUI per se cases, on whether the driver’s BAC reached the statutory threshold. A diagnosis of auto-brewery syndrome may be highly relevant to the source of the alcohol and the prosecution’s interpretation of the evidence, but the legal effect depends on the exact charge and facts of the case.
How do you prove auto-brewery syndrome in a DUI case?
A defendant generally needs objective medical evidence rather than merely asserting that the condition exists. Evidence may include medical records, gastrointestinal testing, cultures identifying ethanol-producing microorganisms, a supervised carbohydrate-challenge test, documentation of earlier unexplained intoxication episodes, and testimony from qualified physicians or toxicologists.
What is a carbohydrate-challenge test?
A carbohydrate-challenge test is a medically supervised procedure used to determine whether a person’s body produces measurable alcohol after consuming carbohydrates without drinking alcohol. Blood or breath alcohol measurements are taken over time while outside alcohol consumption is controlled. The results can provide objective evidence supporting or contradicting an auto-brewery syndrome diagnosis.
Do I need to have been diagnosed before my DUI arrest?
No, but a prior diagnosis or history of documented unexplained intoxication can make the claim easier to support. A diagnosis first made after a DUI arrest may still be legitimate, but prosecutors may scrutinize it more closely. Medical testing and independent evidence connecting the condition to the time of the arrest can become especially important in those cases.
Can I have auto-brewery syndrome without knowing it?
Potentially. Because the condition is rare and its symptoms can resemble ordinary intoxication, some people may experience unexplained dizziness, confusion, fatigue, coordination problems, or other symptoms for a significant period before receiving a diagnosis. Published medical literature has documented delayed diagnoses in some patients.
Can eating carbohydrates trigger an auto-brewery episode?
It can in some people diagnosed with the condition. Carbohydrates can provide material for certain microorganisms in the gastrointestinal system to ferment into ethanol. However, eating bread, pasta, or sugar does not normally cause meaningful intoxication in healthy individuals, so carbohydrate consumption by itself is not evidence that a person has auto-brewery syndrome.
Can auto-brewery syndrome cause someone to fail field sobriety tests?
Yes, if the person is actually experiencing alcohol-related impairment during an episode. Difficulty with balance, coordination, attention, and following instructions could potentially affect field sobriety test performance. Those observations may show impairment, but they do not establish whether the alcohol came from drinking or endogenous production.
Will a police officer believe me if I say I have auto-brewery syndrome?
An officer is not required to accept the claim at the roadside. If the officer observes signs of impairment and obtains evidence supporting DUI, the person may still be arrested. The medical explanation can later be investigated and presented through records, testing, expert testimony, and other evidence.
Can auto-brewery syndrome affect my Colorado DMV case?
Potentially. A medically supported explanation may be relevant at an Expressed Consent hearing, especially when challenging the interpretation of BAC evidence. However, the DMV proceeding is separate from the criminal DUI case, and a medical diagnosis does not automatically prevent an administrative license revocation.
Can an auto-brewery defense challenge a DUI per se charge?
Potentially, although DUI per se cases can be particularly complicated because the statute focuses on the driver’s BAC. Colorado law does allow a defendant to introduce evidence addressing disparities between chemical-test results and other evidence in the case. Medical and toxicological evidence may therefore become important when evaluating how the BAC result should be interpreted.
What experts may be needed in an auto-brewery DUI case?
Depending on the facts, the defense may consult a gastroenterologist, infectious-disease specialist, microbiologist, toxicologist, or other physician familiar with endogenous alcohol production. A medical expert may address the diagnosis while a forensic toxicologist can evaluate the BAC evidence and whether the medical findings could reasonably explain the reported alcohol concentration.
Can an auto-brewery diagnosis explain a very high BAC?
Possibly, but the higher the reported BAC, the more important objective medical evidence may become. Published case reports have documented substantial ethanol levels in some individuals with auto-brewery syndrome, but the condition varies widely. An expert would generally need to determine whether the person’s documented condition could reasonably account for the BAC reported in the specific DUI case.
What if I drank a small amount of alcohol but auto-brewery syndrome increased my BAC?
That situation can be more complicated. The defense may need to determine how much alcohol was intentionally consumed, whether endogenous production also occurred, and whether experts can reliably distinguish between the two sources. The existence of auto-brewery syndrome does not necessarily eliminate the legal significance of alcohol that was knowingly consumed.
Additional Resources
Auto-Brewery Syndrome Information and Research – Auto-Brewery Syndrome Foundation – This organization provides information about auto-brewery syndrome, including symptoms, diagnosis, treatment, ongoing research, and resources for patients and medical professionals. The site can be particularly helpful for understanding how the condition may cause endogenous alcohol production and why specialized medical evaluation is often necessary.
National Library of Medicine – Auto-Brewery Syndrome – This medical overview discusses the causes, symptoms, evaluation, diagnosis, and treatment of auto-brewery syndrome. It also explains the role of carbohydrate-challenge testing and the importance of objectively demonstrating endogenous ethanol production.
PubMed – Endogenous Ethanol Production in the Human Alimentary Tract – This 2025 medical literature review examines endogenous alcohol production, published auto-brewery cases, possible mechanisms, and the medical and legal consequences that can result from delayed diagnosis.
PubMed Central – Endogenous Ethanol Production Literature Review – The full-text review discusses how microorganisms can produce ethanol through fermentation and summarizes documented patients and clinical findings associated with auto-brewery syndrome.
Colorado General Assembly – Colorado Drunk Driving Laws – This state resource explains Colorado DUI, DWAI, DUI per se, BAC presumptions, chemical testing, criminal penalties, and administrative driver’s-license consequences.
Colorado DMV – Alcohol DUI and Driver’s License Consequences – The Colorado DMV explains the separate criminal and administrative processes following a DUI arrest, including BAC-related revocations, Expressed Consent proceedings, and driver’s-license reinstatement requirements.
Colorado DMV – DUI Administrative Hearing Process – This resource explains the seven-day hearing deadline, evidence packets, hearing procedures, burden of proof, and a driver’s ability to present evidence and cross-examine witnesses in an Expressed Consent proceeding.
Colorado Auto-Brewery Syndrome DUI Defense Attorney
Auto-brewery syndrome is rare, and merely claiming that the body produced alcohol will generally not be enough to overcome a Colorado DUI charge. A credible defense ordinarily requires objective medical evidence capable of demonstrating that endogenous ethanol production actually occurs and that the condition could explain the alcohol level involved in the case.
When the evidence supports the diagnosis, however, auto-brewery syndrome can raise unusual questions about the source of the alcohol, the interpretation of chemical-test results, the officer’s assumptions, and the circumstances surrounding the alleged impairment.
A thorough investigation may involve medical records, supervised carbohydrate testing, gastrointestinal testing, blood or breath evidence, toxicology analysis, prior unexplained episodes, witness observations, and testimony from qualified medical experts.
If you have been charged with DUI or DWAI in Colorado despite consuming little or no alcohol, attorney Matthew Martin at The Law Office of Matthew Martin can review the evidence and determine whether auto-brewery syndrome, a testing problem, or another medical explanation may be relevant to your defense.
Call 303.725.0017 today to schedule a free consultation with The Law Office of Matthew Martin.