Breath test numbers look final when they print on the small thermal paper: 0.10, 0.12, sometimes higher. Prosecutors treat those digits like a lock on the case. A seasoned DUI attorney sees something different. Breath results are the end of a chain, and every link in that chain is capable of bending or breaking. When the defense builds from those links, one by one, the picture changes. The number becomes a claim, not a conclusion.
Why the number is not the whole story
Breath alcohol concentration is an estimate derived from a machine that measures alcohol in deep lung air, then uses a conversion ratio to infer blood alcohol concentration. That ratio, commonly 2100 to 1, is an average. Humans are not averages. Physiological differences, temperature variance, and breath technique shape the sample the machine receives. Add in moving parts, calibration drift, software logic, and officer procedure, and you have plenty of places for reasonable doubt.
The legal limit also varies by jurisdiction, and per se laws simplify trials for the prosecution by presuming impairment at a threshold like 0.08. But even in per se cases, the state must prove the machine was accurate, the method was reliable, and the operator followed the rules. That is where effective defense work happens.
The traffic stop and its ripple effect
Breath challenges start before any breath is blown. If the stop was unlawful, everything after it can be suppressed. As a criminal defense attorney, the first files I request are dispatch logs, dash and body camera video, and the officer’s narrative. I compare the stated basis for the stop with the video. Drifting within a lane, for example, is not a crime in many states. A wide right turn may be legal depending on the lane markings. If the initial seizure lacks reasonable suspicion, a motion to suppress can end the case without ever arguing about breath alcohol.
Even when the stop is lawful, the expansion of the stop matters. If the officer turned a minor traffic ticket into a DUI investigation without articulable signs of impairment, subsequent evidence may be excluded. The best Traffic Violations attorney knows that timing, commands, and the sequence of observations on video often tell a different story than what the report suggests.
Field sobriety tests and their limits
Field sobriety tests are used to justify arrest and, later, to validate the breath test. They are not perfect predictors of impairment. The National Highway Traffic Safety Administration (NHTSA) protocols require specific instructions, proper demonstrations, and a flat, dry surface. Shoes, age, weight, and medical conditions also affect performance. A DUI attorney familiar with NHTSA’s manuals will slow down each instruction and each “clue” in court. If the officer failed to ask about injuries or improperly timed the Horizontal Gaze Nystagmus test, that undermines the probable cause to arrest.
This matters for breath results because many jurisdictions require a lawful arrest before an evidentiary breath test. An unlawful arrest can exclude the breath reading entirely.
Instruments are only as good as their maintenance
Breath devices like the Intoxilyzer, Datamaster, or Alcotest rely on precise calibration. Maintenance records, calibration logs, and solution certifications are the backbone of their accuracy claims. Defense lawyers subpoena these records, and when an agency resists, judges often order production, sometimes under protective orders. I look for gaps in calibration dates, service bulletins showing known defects, More help and operator error logs. A single out-of-tolerance control test within the same time window as your test can cast doubt on the entire sequence of results for that instrument.
Different instruments measure alcohol using infrared spectroscopy, fuel cells, or a combination. Each method has known interferences. Infrared devices can be sensitive to compounds like acetone, common in diabetics or low-carb dieters. Fuel cells can be affected by other volatile substances. A thorough criminal attorney checks whether the instrument uses multiple wavelengths to rule out interferents or relies on a single channel susceptible to cross-sensitivity.
Mouth alcohol is the classic trap
Breath machines are designed to sample deep lung air, not residual alcohol in the mouth or throat. Burping, acid reflux, recent use of mouthwash or breath sprays, even chewing tobacco can elevate a reading. That is why most protocols require a continuous observation period before testing, usually 15 to 20 minutes without eating, drinking, vomiting, or belching. In practice, observation is often sloppy. Officers fill out forms in the patrol car, answer radio calls, or assist another driver while the clock ticks.
Two questions matter: did the officer maintain uninterrupted, face-to-face observation for the required time, and did the machine’s slope detector actually detect mouth alcohol? Not all devices have reliable slope detection. I review video to see whether the officer looked away or processed paperwork. If the observation period is compromised, a judge may suppress the result or allow the jury to disregard it.
Breath temperature and hematocrit: science that jurors understand
The partition ratio assuming 2100 to 1 is sensitive to breath temperature. Warmer breath carries more alcohol vapor, increasing the reading. Fever, strenuous exertion, or even a warm environment can nudge readings upward. Some jurisdictions allow expert testimony explaining that a one-degree Celsius increase in breath temperature can raise results by around 6 to 8 percent. In a borderline case, that swing matters.
Physiology plays a role too. People with lower hematocrit levels can have higher breath alcohol readings relative to their true blood alcohol. A Drug Crimes attorney may be familiar with lab values from prior cases and knows how to request medical records or expert evaluations to connect physiology to the breath number.
Interferents and legitimate medical conditions
Not all alcohol-like molecules come from a bottle. Isopropanol used in some products, paint fumes, and certain solvents can show up on a breath test if the instrument lacks proper filtering. People with diabetes can produce more acetone, especially if they are in ketosis. Gastroesophageal reflux disease and hiatal hernias can cause alcohol from the stomach to re-enter the mouth and throat, contaminating a breath sample despite the pre-test waiting period. A careful DUI attorney will:
- Obtain medical history and prescriptions, looking for conditions like GERD, diabetes, or asthma that can affect breath sampling and the ability to provide an adequate sample. Inspect the instrument’s interferent detection capabilities and ask whether officers used any alcohol-based sanitizers or cleaners near the test station.
Protocol deviations that quietly destroy reliability
Police departments publish breath testing manuals that go beyond the statute. Courts often treat those manuals as best practices. Deviations from them erode confidence in the result. Common issues include using expired reference solutions, skipping a second confirmation test, not printing both test results, or failing to switch out a contaminated mouthpiece. In some states, two breath samples must fall within a tight agreement window, for example 0.02 apart, to be valid. If the samples diverge more than allowed, the state may be stuck without a valid result.
A skilled DWI attorney will cross-examine the operator on each step. The questions are simple and hard to dodge: what does the manual require, did you do it, and where is that recorded?
Fermentation in the mouth or sample lines
Dentures, food caught between teeth, or a recent meal can lead to micro-fermentation and create alcohol vapor close to the sensor. Some instruments use heated sample lines to prevent condensation. If those heaters fail, moisture can trap alcohol and later release it into subsequent samples, causing carryover. The fix is not theoretical. I have seen agencies quarantine a device after a cluster of high results were traced to a faulty heater.
The rise of breath test software audits
Breath machines run on firmware, and some manufacturers keep that code proprietary. Litigation in several states has opened the door to limited inspections or audits by defense experts under protective orders. When judges allow it, code reviews have uncovered issues like truncation errors, where the machine discards digits rather than rounding, or algorithms that accept a sample even when breath flow does not meet the standard for deep lung air. These are not glamorous fights, but they can yield leverage in plea negotiations once the prosecutor realizes the agency’s device has unresolved technical questions.
Timing is a defense in its own right
Alcohol absorption and elimination follow predictable, though variable, curves. If you drank shortly before driving, your breath alcohol can be rising during or after the stop. If the first evidentiary test happened 60 to 90 minutes later, the number might reflect a peak that came after you parked. This is the rising BAC defense. It is fact-intensive and benefits from receipts, witness statements, and a careful timeline.
On the other side, if hours pass before testing, elimination may reduce the reading. Prosecutors respond by using retrograde extrapolation, which estimates your earlier BAC based on assumed elimination rates. A defense expert can challenge those assumptions, especially if the state lacks a reliable drinking pattern, body weight, food intake, or starting time.
Refusals, coerced consent, and warrant issues
Not everyone blows. Some refuse, leading to license consequences that vary by state. Even refusals can be challenged when officers misstate the law or issue contradictory warnings. Many jurisdictions require accurate advisement of consequences. If an officer threatens jail for refusing a civil test or implies that silence will be used as evidence of guilt in a criminal sense, the consent can be deemed involuntary.
If police obtain a warrant for a blood draw, chain-of-custody questions, phlebotomy certification, and lab procedures become the battleground. A criminal attorney who handles Drug Crimes and White Collar Crimes understands lab documentation, auditing, and the way errors slip into complex processes. That same skill set applies to forensic blood testing.
Portable breath tests versus evidentiary tests
On the roadside, officers often use small handheld devices. Those are usually preliminary breath testers, not approved for trial on the exact number. They guide the decision to arrest. After arrest, the evidentiary breath test occurs at the station on a larger, calibrated instrument. Mixing the two is common in reports. A defense lawyer will separate them, emphasizing that roadside results are screening tools, not proof beyond a reasonable doubt.
Discovery that pays dividends
Breath cases reward meticulous discovery. Beyond the usual police reports, an experienced defense team requests:
- Instrument-specific maintenance logs, calibration certificates, and solution lot documentation for the weeks surrounding the test date. Operator permits, training records, and any proficiency testing or remedial training notes.
Agencies sometimes balk. That resistance can lead to court orders, sanctions, or, in rare cases, dismissal if the state cannot produce required records. The point is not gamesmanship. If the government asks a jury to trust a number, the defense is entitled to see how that number was produced.
Experts who translate science for jurors
Jurors want to do the right thing, and most will defer to science if it is explained clearly. The defense often retains a forensic toxicologist to discuss partition ratios, breath temperature, and the impact of medical conditions. Some cases call for a gastroenterologist to explain reflux, or a software engineer to discuss firmware. The goal is not to swamp the courtroom with jargon. It is to connect science to common sense. If a person with acid reflux belched during the waiting period, and the officer did not notice because he was filling out a citation, a juror understands how that can skew a breath test.
Plea negotiations shaped by breath challenges
Not every case goes to trial. When the defense identifies concrete issues with the breath result, prosecutors reevaluate. A possible outcome is a reduction to a non-alcohol traffic offense, or an agreement to a treatment-centric resolution, particularly for first-time defendants. Long-term implications matter: insurance premiums, employment, licensing, and immigration status. A traffic ticket attorney who also practices as a DUI attorney can frame a resolution that protects immediate needs and future opportunities.
Collateral consequences and tailored strategies
DUI intersects with other areas of criminal law more often than people think. A driver on probation for a Theft Crimes case, or someone with a pending Domestic Violence charge, faces different risks and incentives. Commercial drivers risk career-ending disqualifications even for administrative findings. A student with a scholarship may face campus discipline apart from court. A criminal defense attorney who also handles embezzlement and Fraud Crimes sees how a DUI can cascade through professional licensing boards that monitor “moral turpitude” or substance-related incidents.
The strategy shifts with the person’s realities. Sometimes the best path is an aggressive suppression motion attacking the stop. Other times it is a frontal challenge to the breath number through experts, followed by trial. In some cases, the smartest move is early mitigation: treatment, ignition interlock, and proactive community service that humanizes the defendant and demonstrates responsibility.
Real-world examples that show the range
I once reviewed a case where the instrument logged an “invalid sample” followed within minutes by a passing control test and then a 0.11 reading. The operator testified that the defendant failed to blow hard enough on the first try. Maintenance logs revealed a series of invalids that week, and a later technician note identified a faulty flow sensor. The prosecutor offered a reduction to reckless driving before the hearing ended.
Another case turned on video. The officer claimed a 20-minute observation period. The body camera showed the officer stepping into the hallway for several minutes while the defendant sat alone, coughing and spitting into a trash can. The trial judge suppressed the breath test for failure to follow mandatory protocol. The state proceeded on testimony and field tests alone, and the jury returned a not guilty after 30 minutes of deliberation.
A third case involved a client with Type 1 diabetes. Hospital records from the following day showed high ketone levels. Our expert explained how acetone can be misread by certain infrared devices if the instrument does not employ multiple filters. The jury did not trust the 0.09 reading and acquitted.
The role of cross-examination
Cross-examination is less about gotchas and more about clarity. The best questions are short. They restate the protocol and anchor the witness to it. If the manual says two breath samples must be within a specified range, and the officer cannot explain why one sample was discarded without documentation, credibility erodes. If the officer cannot confirm whether the reference solution was at the proper temperature, the jury registers uncertainty. A DWI attorney with trial experience in Assault and Battery or burglary cases brings the same discipline to technical cross, but with a focus on simplifying, not dramatizing.
Administrative hearings and how they help the criminal case
License suspension hearings operate under different rules, often with shorter deadlines and lower burdens of proof. Even if the odds are tough, these hearings can be gold mines for testimony. Officers show up without the full polish of a criminal trial, and transcripts capture admissions about observation gaps, instrument quirks, and incomplete notes. Later, those statements box in the witness at trial. A lawyer who handles both the administrative and criminal sides uses the first to sharpen the second.
When blood tests enter the picture
Some agencies prefer blood draws for suspected drugged driving or when the breath machine is down. Blood tests feel more authoritative, but they carry their own vulnerabilities: chain-of-custody errors, improper preservatives, fermentation in the vial if not sealed correctly, and lab backlogs that invite mistakes. If you face both drug possession and DUI allegations, a drug possession attorney will scrutinize the seizure and lab processes from a different angle, sometimes uncovering issues that cross-pollinate and benefit the DUI defense.
Jury education without lecturing
A trial is a story. Breath numbers risk shrinking that story to a single plot point. The defense opens it back up. We talk about time: when the client drank, when the car was stopped, when the tests were administered. We talk about place: the slope of the road during field tests, the busy station where the operator juggled multiple tasks. We talk about people: a nervous driver who hyperventilated, an officer who meant well but skipped a step, a technician who wrote a warning about calibration drift that never made it into training. Jurors lean in when the details feel real, and they punish overconfidence that is not backed by careful work.
How to prepare if you have a breath test case
Preparation is the antidote to panic. Save receipts that show timelines. Write down exactly what you ate and drank, with times, within hours of the stop. Note any burping, vomiting, or heartburn symptoms around the test. Identify witnesses who saw you before driving. Gather medical records if you have reflux, diabetes, or respiratory issues. Bring your driving history, insurance, and any professional licenses to the consultation, because collateral consequences shape strategy. And act quickly. Deadlines for administrative hearings are tight, sometimes as short as 10 days.
Myths worth letting go
Police sometimes imply that breath machines are infallible. They are not. Defendants sometimes believe that if the number is high, there is nothing to do. That is also untrue. There are cases where the machine is right and the evidence is strong, and an honest DUI attorney will say so. But many cases sit in the middle, where nuance, diligence, and smart lawyering make the difference between a damaging conviction and a manageable outcome.
Choosing the right advocate
Look for experience with breath litigation, not just plea bargaining. Ask to see samples of motions on observation periods, calibration record subpoenas, and challenges to rising BAC. Find out whether the lawyer has tried cases involving technical evidence, whether as a DWI attorney, a Fraud Crimes attorney who handles forensic accounting, or a gun possession attorney familiar with lab analysis of firearms residue. Breadth is helpful when the defense turns on procedures, records, and expert testimony.
A firm that covers related areas, from grand larceny to petit larceny, trespass, criminal mischief, or even homicide, often has a bench of litigators who know how to cross-examine and how to build a record for appeal. Specialized knowledge matters, but so does courtroom craft.
The bottom line
Breathalyzer results are not verdicts. They are measurements produced by machines, operated by people, within systems that work well on most days and poorly on others. A criminal defense attorney who treats the number as a starting point, not an ending, can exploit weak links: unlawful stops, flawed field tests, incomplete observation periods, calibration gaps, software and hardware issues, medical realities, and procedural missteps. With that approach, what looked like a closed door becomes an open case, and sometimes, a second chance.
Michael J. Brown, P.C.
(631) 232-9700
320 Carleton Ave Suite No: 2000
Central Islip NY, 11722
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