Why a Massachusetts Breathalyzer Result Does Not Establish Guilt Beyond a Reasonable Doubt

By Attorney Joe Serpa | Georgetown University Law Center | 30 Years Massachusetts Criminal Defense

A breathalyzer reading of .08 or higher establishes a per se violation of M.G.L. c. 90, § 24(1)(a)(1). It does not establish guilt beyond a reasonable doubt. The statute gives the Commonwealth two theories, operation with a blood alcohol percentage of .08 or greater and operation while under the influence of intoxicating liquor. Massachusetts courts treat breath test results as scientific evidence subject to foundational challenge, and the Commonwealth’s documented institutional failures at its own Office of Alcohol Testing have given defense attorneys substantial grounds to contest both the admissibility and the reliability of Draeger Alcotest 9510 results. A reading from a police station breathalyzer is the beginning of the evidentiary analysis, not the end of it.

Many of these matters can be resolved well before trial. See how criminal cases actually get dismissed in Massachusetts.

The Draeger Alcotest 9510 and the Regulatory Framework

The Draeger Alcotest 9510 is the breath test device the Office of Alcohol Testing (OAT) has approved and deployed for evidentiary use in Massachusetts, replacing the older Alcotest 7110 beginning in 2011. Its administration is governed by 501 CMR 2.00, the Safe Roads regulations issued under M.G.L. c. 90, § 24K through the Executive Office of Public Safety and Security. Under 501 CMR 2.04, OAT maintains the approved device list, certifies each machine annually, and trains and certifies the operators. The regulations set specific requirements for machine certification, operator certification, the observation period, and the internal consistency of the two required breath samples.

A result produced in violation of those requirements can be excluded on a defense motion, because regulatory compliance is the foundation for admitting the number at all. The stop, the exit order, and the arrest that preceded the test face separate constitutional scrutiny under the Fourth Amendment and Article 14 of the Massachusetts Declaration of Rights. The firm’s pages on Illegal Searches and Seizures in Massachusetts and Massachusetts traffic stops, exit orders, and pretext searches explain those challenges.

The Roadside Portable Breath Test Is Inadmissible at Trial

The portable breath test (PBT) administered on the roadside is strictly inadmissible at trial in Massachusetts as evidence of BAC. Handheld roadside devices do not meet the reliability standards of 501 CMR 2.00 and are not approved by the Office of Alcohol Testing for evidentiary use. An officer may use the PBT result to establish probable cause for an arrest, but the number cannot be presented to a jury. Only the station-house Draeger Alcotest 9510 result, when properly administered, is admissible at trial. The firm’s guide Should I Take the Breathalyzer in Massachusetts? covers that roadside decision.

Refusal Evidence Is Inadmissible at Trial

A driver who declines the breathalyzer does not hand the prosecution a trial exhibit. M.G.L. c. 90, § 24(1)(e) makes refusal evidence inadmissible against the defendant. The Supreme Judicial Court explained why in Opinion of the Justices, 412 Mass. 1201 (1992). A refusal reveals the driver’s thought process about how the test might come out, which makes it testimonial, and using it at trial would violate the Article 12 privilege against self-incrimination. The jury is never told a test was offered and declined. A refusal does trigger a Registry of Motor Vehicles suspension on a separate track from the criminal case, as the Massachusetts OUI license FAQs explain.

The 15-Minute Continuous Observation Period

Under 501 CMR 2.13(3), a certified breath test operator must observe the arrestee for no less than 15 minutes immediately before the Draeger Alcotest 9510 test. The purpose is to let mouth alcohol dissipate. Regurgitation, belching, or anything placed in the mouth can push stomach alcohol into the upper airway and artificially inflate the result, and the regulation requires the observation period to restart when that happens. The requirement is not a suggestion. It is a regulatory precondition to a valid test, and a violation is grounds for a motion to exclude the entire result.

A break in the observation matters. Stepping out of the room, attending to another detainee, or looking away for a sustained period undermines the foundation for the test. Booking room video and the observation log in the officer’s report are the primary sources for this challenge. In busy booking rooms from Woburn to Quincy, officers handling paperwork, phones, or other detainees during the observation period is not unusual. Serpa Law Office demands booking room video in every OUI case.

Commonwealth v. Ananias and the Calibration Records Requirement

The most significant development in Massachusetts breathalyzer litigation was the consolidated Commonwealth v. Ananias litigation, in which District Court Judge Robert Brennan heard challenges on behalf of OUI defendants statewide. In February 2017 the court found that OAT’s annual certification methodology from June 2011 through September 2014 was unreliable because the office had no written certification protocols. Later that year the litigation exposed something worse. OAT had withheld failed calibration worksheets the discovery order required it to produce, and the parties ultimately stipulated that the office intentionally withheld 432 of them.

The consequences were sweeping. Draeger Alcotest 9510 results from tests conducted between June 1, 2011 and April 18, 2019 became presumptively excluded, and courts ordered notice to more than 27,000 defendants. It stands as one of the largest exclusions of forensic evidence in Massachusetts history, and the problems did not end in 2019. Judge Brennan suspended the use of 9510 results statewide again on November 15, 2021 after further disclosure failures surfaced, then vacated that suspension in January 2022. In Commonwealth v. Hallinan, 491 Mass. 730 (2023), the Supreme Judicial Court held that every defendant whose case included a 9510 result from the excluded window receives a conclusive presumption of egregious government misconduct when moving for a new trial or to withdraw a plea, though the defendant must still show a reasonable probability that knowing of the misconduct would have changed the decision to plead.

The Ananias litigation also established what the defense is entitled to in every case. Defense counsel may demand the complete calibration and maintenance records for the specific Draeger machine used in the defendant’s arrest, including any failed calibration cycles, diagnostic error messages, and annual certification data. A machine that was not properly certified, that has a history of interferent-detected error messages, or that failed prior calibrations does not produce a reliable result. Serpa Law Office demands these records in every case. The prosecution’s assurance that the machine was properly calibrated is not a substitute for the documentation.

Commonwealth v. Camblin and the Right to Challenge the Machine

The right to attack the machine itself is settled law. In Commonwealth v. Camblin, 471 Mass. 639 (2015), the Supreme Judicial Court held that a defendant may challenge the scientific reliability of the breath test device, including its source code, and it ordered a full reliability hearing on the older Alcotest 7110. After the hearing on remand, the court concluded in Commonwealth v. Camblin, 478 Mass. 469 (2017) that the Alcotest 7110 produced reliable results. The defense lost that round on the facts, but the principle matters more. Breath test evidence receives no automatic presumption of validity, and a defendant may put the machine itself on trial.

The .02% Internal Consistency Requirement

501 CMR 2.14 requires the Draeger Alcotest 9510 to capture two adequate breath samples during a single test sequence, and the two readings must agree within plus or minus 0.02 blood alcohol content units. If the first sample reads .09 and the second reads .12, the pair is out of tolerance, and the machine is supposed to begin a new test sequence rather than report a result. The sample readings appear on the breath test printout, and the defense reviews them in every case. When the printout shows a variance beyond the tolerance or irregularities in the sequence, a motion to exclude the result is available because the test failed the regulation’s own requirements.

Medical Conditions That Can Affect the Result

Certain medical conditions can artificially inflate a Draeger Alcotest 9510 result by putting compounds into the breath sample that the machine can misread as ethanol. Gastroesophageal reflux disease (GERD) and acid reflux can push stomach alcohol into the upper airway through acid regurgitation, producing the same distortion as a breach of the observation period. Diabetes and certain metabolic conditions produce ketones and acetone, and defense experts contend that infrared breath testing can partially misread those compounds. Medication effects on a defendant’s breath chemistry can be developed the same way.

When a defendant has any of these conditions, the defense develops expert testimony and medical records to challenge the specific result. Defense experts contend that the machine cannot fully distinguish ethanol from certain chemically similar compounds and that the regulatory framework ignores individual physiological variation. That challenge is built case by case, on this defendant’s medical history and this machine’s records.

The Rising BAC Defense

Alcohol is absorbed into the bloodstream over time. The rate depends on the type and quantity of alcohol consumed, the food in the stomach, the defendant’s body weight, and individual metabolic factors. A person who stopped drinking an hour before driving may keep absorbing alcohol through the traffic stop, the field sobriety tests, the transport to the station, and the 15-minute observation period. That driver can register above .08 at the breath test even though the BAC while actually driving was below the legal limit.

The rising BAC defense depends on specific facts. It requires documentation of the timing of the last drink, the quantity consumed, the time of the traffic stop, and the time of the breath test. When those facts support the argument, expert testimony on alcohol pharmacokinetics can establish that the BAC while driving was below .08 even though the station-house reading came in above it. The firm’s post on how Massachusetts OUI cases are won at trial shows this defense in action.

What Happens If the Breathalyzer Result Is Admitted

When the breathalyzer result survives the pretrial challenges and is admitted, the defense continues. A .08 reading is not an automatic conviction. It is one piece of evidence the jury must weigh against everything else. Body camera footage showing the defendant speaking clearly, answering questions coherently, and walking without difficulty directly contradicts the characterization of the defendant as impaired. Dash camera footage showing controlled, lawful driving before the stop is similarly relevant. Witness testimony from passengers who observed the defendant throughout the evening is available when it exists.

Juries are not required to accept a machine reading as conclusive. The prosecution must prove its case beyond a reasonable doubt on the totality of the evidence. Attorney Serpa has tried OUI cases in which the admitted breathalyzer result was .11, .13, and higher and secured not-guilty verdicts in each of them. The firm’s Massachusetts Criminal Defense Trial Results page collects those outcomes. On a first offense, a continuance without a finding paired with the Section 24D alcohol education program can still resolve the case without a conviction. The firm’s page on what a CWOF is and how it works explains that disposition. The result is the beginning of the trial defense, not the end of it.

Key Takeaways

• The roadside portable breath test (PBT) result is inadmissible at trial in Massachusetts. It cannot be shown to a jury as evidence of BAC.
• Evidence that a driver refused the breathalyzer is inadmissible at trial under M.G.L. c. 90, § 24(1)(e). The jury never hears about a refusal.
• 501 CMR 2.13(3) requires a 15-minute observation period immediately before the Draeger Alcotest 9510 test. A break in that observation is grounds for a motion to exclude the result.
• The Commonwealth v. Ananias litigation presumptively excluded Draeger 9510 results from June 1, 2011 through April 18, 2019, and Commonwealth v. Hallinan, 491 Mass. 730 (2023) gives affected defendants a conclusive presumption of egregious government misconduct.
• Calibration and maintenance records for the specific machine used in the defendant’s arrest must be demanded and reviewed in every case.
• If the two required breath samples disagree by more than 0.02 blood alcohol content units, the test fails its own tolerance under 501 CMR 2.14.
• Medical conditions including GERD, acid reflux, and diabetes can artificially inflate a Draeger Alcotest 9510 result. Expert testimony and medical records are available to challenge specific results.
• A breathalyzer result admitted into evidence is not an automatic conviction. Body camera footage, dash camera footage, and witness testimony remain relevant at trial.

Serpa Law Office represents defendants in OUI cases across the Massachusetts District Courts and Boston Municipal Court. Attorney Joseph Serpa is a Georgetown Law graduate with thirty years of Massachusetts criminal defense experience and a perfect record of not-guilty verdicts in OUI jury trials. Contact Serpa Law Office at 617.936.0201 for a free consultation. The Boston office is at 20 Park Plaza #400A and the Quincy office is at 500 Victory Rd., Suite 400A. The firm is available 24 hours a day.

Related Resources

• OUI Defense in Massachusetts, Main Practice Area Page
• Should I Take the Breathalyzer in Massachusetts?
• Massachusetts OUI License Suspensions
• Massachusetts OUI FAQs
• Fighting an OUI in Massachusetts, How Cases Are Won at Trial
• What Happens After an OUI Arrest in Massachusetts
• Illegal Searches and Seizures in Massachusetts
• CWOF, Pretrial Probation, and Diversion in Massachusetts FAQs
• Criminal Defense for Licensed Professionals in Massachusetts
• Immigration Consequences of Massachusetts Criminal Charges
• Massachusetts Criminal Defense Trial Results
• Boston Municipal Court
• Quincy District Court
• Cambridge District Court
• Dedham District Court
• Woburn District Court