Countering Blood Alcohol Content Evidence in Dram Shop Cases

Blood alcohol content evidence often serves as the cornerstone of dram shop liability claims, with plaintiffs pointing to a BAC reading to argue that a patron was obviously intoxicated when alcohol was served. That reading, however, is rarely as conclusive as it may first appear, and it can be tested on scientific, procedural, and legal grounds that go far beyond the number on a lab report. Establishments that understand where BAC evidence is vulnerable are better positioned to respond when a claim is filed, whether that means challenging the science behind the number, the paperwork behind the sample, or the legal standard the plaintiff must actually meet.

At Fahl & Donaldson, our dram shop liability defense attorneys work with bars, restaurants, and other alcohol-serving establishments throughout Texas to examine how BAC evidence was collected, tested, and interpreted before it is ever presented to a judge or jury. Effective defense in this area requires legal knowledge paired with a working understanding of how alcohol moves through the body, how BAC testing methods differ, and how a lab result can produce a picture that does not match what a server actually observed at the time of service.

The Scientific Limits of BAC Evidence in Dram Shop Cases

Blood alcohol content testing involves scientific processes that are subject to error and contamination at several stages. The timing of the draw, the storage conditions of the sample, and the laboratory procedures used to analyze it can all affect reliability. Many people assume a BAC number is infallible, but multiple factors can compromise accuracy long before a result reaches a courtroom.

Testing methods also matter. A breath test measures alcohol in exhaled air and estimates a corresponding blood concentration, while a blood draw measures alcohol directly in a sample sent to a laboratory. Each method carries its own sources of error, from mouth alcohol contamination and improper breathing technique on a breath test to hemolysis, fermentation, or improper anticoagulant use in a blood sample. Neither method is immune from mistakes made by the person administering the test or the equipment used to run it.

The relationship between a BAC reading and actual impairment also varies significantly from person to person, based on body weight, food consumption, medication use, and individual alcohol tolerance. According to MedlinePlus, a consumer health resource maintained by the National Library of Medicine, the timing of a blood alcohol test relative to the last drink can itself affect the accuracy of the result. A person with an identical BAC reading may present very differently depending on these variables, which is part of why a lab number alone rarely tells the whole story of how a patron appeared at the time of service. The firm’s overview of Houston dram shop liability statistics offers additional context on how frequently these claims turn on contested evidence rather than undisputed fact.

Chain of Custody Issues

Proper chain of custody documentation is essential to BAC evidence admissibility. Any break in the documented handling of a blood sample, from collection through testing, can provide grounds to challenge or exclude it. This includes improper labeling, storage temperature violations, or gaps in the transfer records between law enforcement, medical facilities, and testing laboratories. A complete chain of custody log typically documents who collected the sample, how it was sealed, every person who handled it afterward, and the conditions under which it was stored and shipped. Defense counsel should scrutinize every step of that handling process for procedural errors, since a documented gap in custody, or a missing signature on a transfer log, can undercut the reliability of the entire test. Requesting the complete custody file early in a case, rather than relying on a summary lab report, is often the only way to confirm whether the underlying paperwork actually supports the number a plaintiff intends to rely on.

The Raoger v. Myers Decision and the Obvious Intoxication Standard

Texas dram shop law has always required proof that a patron’s intoxication was apparent to the provider at the time alcohol was served, not simply that the patron was intoxicated at some later point. In April 2025, the Texas Supreme Court addressed how far circumstantial evidence, including a post-incident BAC reading, can go in meeting that standard. In Raoger Corporation v. Myers (Texas Supreme Court, No. 23-0662), the court held that evidence requiring “inferences upon inferences,” such as extrapolating backward from a BAC test taken after an incident to what a patron’s condition must have looked like at the time of service, is not enough on its own to establish obvious intoxication.

This decision may give defense counsel a stronger framework for challenging claims that rely primarily on a BAC number rather than direct observational evidence of how a patron actually appeared while being served. Direct evidence typically means firsthand accounts, such as server or bartender testimony, surveillance footage, or contemporaneous statements describing specific signs of impairment like slurred speech, unsteady movement, or the smell of alcohol. In many cases, the absence of that kind of direct, contemporaneous evidence can support summary judgment arguments or narrow the scope of expert testimony a plaintiff is permitted to offer.

Because this is a relatively recent development, establishments facing a dram shop claim in Texas may want to discuss with counsel how the decision applies to the specific facts and timeline of their case, particularly where the only evidence of intoxication comes from testing performed well after the patron left the premises.

Challenging Testing Procedures and Timing

The timing of BAC testing relative to alcohol service presents a significant defense opportunity. Blood alcohol levels continue to rise for a period after consumption stops, meaning a person’s BAC at the time of testing may be higher than it was during service at an establishment. This concept, often called rising blood alcohol, can be significant in dram shop cases where hours passed between the last drink served and the test itself. The longer that gap, the more room exists to argue that the tested result reflects continued absorption rather than the patron’s actual condition while still at the establishment.

Laboratory testing procedures must also follow strict protocols to help ensure accuracy. Calibration of testing equipment, proper sample preparation, and adherence to quality control measures can all affect reliability. When a plaintiff relies on a retrograde extrapolation calculation, meaning an estimate of what a patron’s BAC must have been at an earlier point in time, that calculation depends on assumptions about absorption and elimination that can vary considerably between individuals. Defense teams can request documentation of testing procedures, equipment calibration logs, and the underlying assumptions behind any extrapolation to help identify potential sources of error in a given case.

Environmental and Medical Factors

Environmental and medical factors can affect BAC test results in ways that may not reflect actual impairment during alcohol service. Medical conditions such as diabetes or gastroesophageal reflux disease, along with certain medications, can interfere with testing accuracy, and environmental factors, including temperature exposure or sample contamination, can skew results as well. Some individuals also produce naturally elevated readings on breath tests due to conditions affecting digestion or metabolism, which can create a false impression of a higher BAC than blood testing would confirm. These factors become particularly relevant when the goal is to separate a lab number from the level of intoxication that was actually observable to servers at the time of service. Medical records and, where appropriate, a treating physician’s records or an independent medical review can help establish whether a documented condition or medication was present and capable of affecting the result.

Establishing Alternative Explanations

Effective dram shop defense often involves presenting alternative explanations for intoxication evidence that do not implicate an establishment’s own service practices. This can include alcohol consumed at other locations after a patron left the establishment, medications that intensify the effects of alcohol, or medical conditions that produce symptoms resembling intoxication. Reviewing what a patron did and how they appeared before arriving can be just as important to a defense as reviewing what happened once they were on the premises, a theme explored further in the firm’s discussion of evidence needed to challenge intoxication claims in dram shop cases.

Documentation of a patron’s activities and condition before arriving at an establishment can provide important context for BAC evidence. Security footage, witness statements, receipts, and transaction records from other locations can help show that observable intoxication resulted from alcohol consumed elsewhere rather than from service at the business being sued. Gathering this documentation often means promptly requesting records from nearby establishments, rideshare or taxi services, and any other source that can help reconstruct the patron’s timeline before and after leaving the premises. The sooner this outreach begins after an incident, the more likely it is that records still exist and that witnesses can recall specific details rather than a general impression of the evening.

Scientific Expert Testimony

Challenging BAC evidence often calls for qualified expert testimony to explain testing limitations and alternative interpretations of results to a judge or jury. Toxicology experts can address absorption rates, elimination rates, and the relationship between a BAC level and the observable impairment symptoms a server would reasonably notice in the moment. Selecting a witness with the right credentials, such as board certification in forensic toxicology or clinical pharmacology, and preparing that witness to explain complex science in plain terms, is often central to whether a jury finds the testimony persuasive. As the Raoger decision illustrates, courts are paying closer attention to whether that kind of testimony crosses the line from reasonable inference into speculation, which makes the selection and preparation of a qualified expert an important part of the defense.

Texas courts have long applied a reliability standard, sometimes referred to as a Robinson challenge after the Texas Supreme Court case that established it, to determine whether expert testimony is admissible in the first place. A motion challenging the reliability of a plaintiff’s toxicology or extrapolation expert can be filed before trial, and if successful, can narrow or eliminate the scientific basis for a claim that otherwise depends heavily on a BAC number. Defense counsel can use this procedural tool alongside, rather than instead of, direct challenges to the underlying test results themselves.

BAC Evidence and the Statutory Safe Harbor Defense

Attacking the reliability of BAC evidence is not the only path available to an establishment facing a dram shop claim in Texas. Separate from any argument about testing accuracy or chain of custody, Texas law provides a statutory Safe Harbor defense for establishments whose employees have completed a certified seller training program and where there is no evidence the establishment knowingly served an obviously intoxicated patron. These two lines of defense often work together rather than as alternatives to one another.

A BAC reading that raises questions about testing reliability can help undercut a plaintiff’s claim that intoxication was obvious, while documentation that staff completed TABC-approved training can support the separate statutory defense even if a court accepts some version of the BAC evidence. Establishments that keep both types of records, testing and custody documentation on one hand, and training and certification records on the other, are generally in a stronger position no matter which theory a case ultimately turns on.

Building a Defense Strategy Around These Evidentiary Gaps

None of these evidentiary weaknesses operates in isolation, and the strongest dram shop defenses typically combine several of them into a single, coherent strategy built around the records an establishment already keeps or can reasonably start keeping. A few of the building blocks include:

• Documented service records. Point of sale data, timestamps, and staff accounts of what was actually served can anchor a timeline independent of a later BAC reading.
• Verified identification practices. Establishments that can show ID checks were properly performed strengthen the broader defense narrative around responsible service.
• Staff training records. Documentation that staff completed recognized training to avoid dram shop liability claims can support a defense that observable intoxication was not apparent at the time of service.
• Independent witness accounts. Security footage and third party witnesses can corroborate, or contradict, a plaintiff’s account of how a patron appeared while on the premises.
• Prompt incident documentation. Recording what staff observed as soon as possible after an incident helps preserve details that fade quickly from memory.

Establishments that maintain these records as a matter of course, rather than scrambling to reconstruct them after a claim is filed, are generally better positioned to challenge BAC evidence when a dispute arises, an approach discussed more broadly in the firm’s overview of defending bars and restaurants against over-service claims.

Frequently Asked Questions About BAC Evidence in Dram Shop Cases

Contact Fahl & Donaldson for Strategic Dram Shop Defense

Countering BAC evidence calls for an approach that treats the science and the law as equally important pieces of the same defense. The attorneys at Fahl & Donaldson bring decades of civil litigation experience to matters involving business litigation and alcohol-related liability claims, and the firm works closely with qualified toxicology and forensic experts when a case calls for it. Our approach centers on identifying the specific evidentiary and procedural weaknesses present in each case, from testing methodology to chain of custody to the observational evidence available from the night in question, rather than applying a one-size-fits-all defense. We also stay current on developments like the Raoger decision so that the defense strategy reflects where Texas dram shop law stands today, not where it stood when a claim was first filed.

If your restaurant, bar, or other establishment is facing a dram shop claim that relies on blood alcohol content evidence, an early conversation with counsel can help identify which of these defense strategies may apply to your situation and what records should be preserved right away. Reach out through our contact form to discuss the specifics of your case, including what documentation to preserve while the matter is still active.