Fighting an OUI in Massachusetts: How Cases Are Won at Trial

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

I maintain a perfect record of not guilty verdicts in OUI jury trials in the Massachusetts District Courts and Boston Municipal Court. I built that record over thirty years in courtrooms across Eastern Massachusetts. In this post I explain how Massachusetts OUI cases are won, from the initial stop through jury deliberations, and what the defense must do at each stage to give the defendant the best available outcome.

The trial preparation described here, and the alternatives when trial is not the right path, are covered on dismissals and not guilty verdicts.

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

The Prosecution’s Burden

Under M.G.L. c. 90, § 24, the Commonwealth must prove guilt beyond a reasonable doubt, the highest standard in the legal system. An OUI conviction under § 24(1)(a)(1) requires three elements. The Commonwealth must prove that the defendant operated a motor vehicle, and that the operation occurred on a public way or in a place to which the public has a right of access. It must then prove impairment in one of two ways, either that the defendant was under the influence of intoxicating liquor or drugs, or that the defendant’s blood alcohol percentage was .08 or greater.

A breathalyzer result is not proof of guilt. An officer’s opinion that the defendant seemed impaired is not proof of guilt. Each element of the offense must be established by admissible evidence, and each piece of admissible evidence is subject to challenge. The defense’s task is to identify the weakest point in the prosecution’s case and develop it fully, from the first day of representation through the jury verdict.

Layer 1: The Constitutionality of the Stop

Before any other evidence matters, the traffic stop must have been constitutionally lawful. Under the Fourth Amendment and Article 14 of the Massachusetts Declaration of Rights, an officer must have reasonable articulable suspicion of a motor vehicle violation or criminal activity before initiating a stop. A stop based on a hunch, an anonymous tip without corroboration, or a violation the officer misidentified is unconstitutional. See Illegal Searches and Seizures in Massachusetts and the Massachusetts Traffic Stop FAQs.

Evidence obtained from an unconstitutional stop is suppressible in its entirety through a Motion to Suppress. That includes the officer’s observations, the field sobriety test results, and the breathalyzer result. When the suppressed evidence is the totality of the prosecution’s case, dismissal follows. I have obtained dismissals at the motion stage in OUI cases involving BAC readings of .11, .13, and higher, where the stop that led to those readings was constitutionally defective. The full stop framework, updated for Commonwealth v. Arias, the April 2026 SJC decision suppressing a stop made a day after the observed infraction, is at Massachusetts Traffic Stops, Exit Orders, and Pretext Searches. The role of phones, GPS records, and license plate readers is covered in The Modern Massachusetts Traffic Stop.

Dash camera footage, body camera footage, and the officer’s written report are the primary sources for a suppression motion. They are demanded in every case before any motion deadline passes.

Layer 2: The Field Sobriety Tests

The three Standardized Field Sobriety Tests, Horizontal Gaze Nystagmus (HGN), Walk and Turn (WAT), and One Leg Stand (OLS), are voluntary in Massachusetts and carry no license suspension penalty if refused. When administered, they must be conducted in strict compliance with National Highway Traffic Safety Administration (NHTSA) guidelines. The required lighting levels, surface conditions, pre-test verbal instructions, and clue-scoring criteria are all specified in NHTSA protocols and must be followed exactly.

Any deviation from protocol is grounds for a motion to exclude the test results or aggressive cross-examination of the administering officer at trial. Body camera and dash camera footage routinely contradict an officer’s field sobriety scoring. A defendant the officer scored as failing the Walk and Turn who can be seen on video walking a steady line and turning correctly is a powerful trial exhibit. These materials are demanded in every case.

The Supreme Judicial Court also limits how this evidence reaches a jury. In Commonwealth v. Gerhardt, 477 Mass. 775 (2017), the court held that in marijuana OUI cases these roadside exercises must be described as roadside assessments rather than as scientific tests. The officer may describe the driver’s balance, coordination, and mental acuity, but may not testify that the driver passed or failed, and no witness who is not a qualified expert may offer an opinion that a driver was under the influence of marijuana. The court also required a jury instruction that performance on roadside assessments, standing alone, is never enough to convict in a marijuana case.

Non-alcohol-related causes of HGN nystagmus, inner ear conditions, and fatigue are available as cross-examination material when the officer relies heavily on the HGN test. The OLS and WAT results are similarly subject to challenge when the testing surface was uneven, when the defendant was wearing heels, or when the pre-test instructions were not given correctly. See Massachusetts OUI Defense.

Layer 3: The Breathalyzer

The Draeger Alcotest 9510 is the only breathalyzer approved for evidentiary use in Massachusetts under 501 CMR 2.00. A result at or above .08 establishes a per se violation of M.G.L. c. 90, § 24. It does not establish guilt beyond a reasonable doubt. The result is subject to challenge on multiple grounds, examined in every case.

The 15-minute observation period. Before administering the Alcotest, the breath test operator must observe the defendant for no fewer than 15 minutes under 501 CMR 2.13 to ensure no mouth alcohol is introduced. Any break in that observation, leaving the room, attending to another person, or looking away, is grounds for a Motion to Suppress the entire result. The 15-minute log in the officer’s report and the booking room video are the primary sources for this challenge.

Calibration and maintenance records. The consolidated Commonwealth v. Ananias litigation in the District Court exposed the Office of Alcohol Testing withholding hundreds of failed calibration worksheets from defense counsel. The courts responded by presumptively excluding Alcotest results from tests administered between June 1, 2011 and April 18, 2019, and more than 27,000 defendants received notice that their cases were affected. In Commonwealth v. Hallinan, 491 Mass. 730 (2023), the SJC completed that framework and gave defendants who had already pleaded guilty a conclusive presumption of egregious government misconduct. Tests after April 18, 2019 are no longer presumptively excluded, so the calibration and maintenance records of the specific Draeger machine used in the arrest are demanded in every case. A machine that was not properly calibrated or maintained does not produce a reliable result.

The 0.02 internal consistency requirement. 501 CMR 2.14 defines a valid breath test as one adequate breath sample, a calibration standard analysis, and a second adequate breath sample, and the two breath samples must agree within 0.02 blood alcohol content units. When they do not, the sequence is invalid and a new sequence must begin. The two readings appear in the breath test record and are reviewed in every case.

Medical conditions. Gastroesophageal reflux disease (GERD), acid reflux, diabetes, and certain medications can artificially inflate a breathalyzer reading through mouth alcohol contamination or acetone production. When a defendant has any of these conditions, the defense develops expert testimony and medical records to challenge the reliability of the specific result.

The rising BAC phenomenon. Alcohol continues to absorb into the bloodstream after consumption. A person who stopped drinking an hour before driving and was below .08 while operating may have continued absorbing alcohol through the arrest and the 15-minute observation period, registering above .08 at the time of the breath test. The timing of the last drink, the quantity consumed, the defendant’s body weight, and the time of the breath test are all relevant to a rising BAC defense.

The right to an independent examination. A person held on an OUI charge has a statutory right under M.G.L. c. 263, § 5A to be examined immediately, at his own expense, by a physician of his own choosing. The police must inform the defendant of that right and give a reasonable opportunity to exercise it. When they deny or frustrate that opportunity, the defendant loses independent proof of sobriety, and the remedy can extend to dismissal.

A defendant who declined the breath test faces a different calculus, and the jury never learns of the refusal. M.G.L. c. 90, § 24(1)(e) makes evidence of a refusal inadmissible in any criminal proceeding, and in Opinion of the Justices, 412 Mass. 1201 (1992), the SJC concluded that admitting refusal evidence would violate the privilege against self-incrimination under Article 12 of the Massachusetts Declaration of Rights because a refusal is testimonial in nature. For a complete analysis of breathalyzer challenges, see Why a Failed Breathalyzer Does Not Equal an OUI Conviction in Massachusetts.

Layer 4: The Trial

When motions are denied and the case proceeds to trial, the defense continues. An OUI jury trial in Massachusetts District Court is typically a one-day proceeding. The jury is composed of six jurors under M.G.L. c. 218, § 26A. The defense cross-examines the arresting officer and any other prosecution witnesses, moves to exclude specific pieces of evidence, and presents its own witnesses and exhibits.

Massachusetts law limits what the arresting officer may tell that jury. Under Commonwealth v. Canty, 466 Mass. 535 (2013), an officer may offer a lay opinion about the defendant’s apparent level of sobriety or intoxication, but may not opine that the defendant operated under the influence or that alcohol diminished the defendant’s ability to drive safely. Those ultimate questions belong to the jury alone, and effective cross-examination holds the officer to that line.

The most effective OUI trial defense presents the jury with a complete factual picture that the prosecution’s evidence does not capture. Booking room video showing the defendant speaking clearly, walking without difficulty, following instructions, and appearing coherent directly contradicts the officer’s characterization of the defendant as impaired. Dash camera footage showing controlled, lawful driving before the stop contradicts the impairment theory. Witness testimony from passengers or bystanders who observed the defendant before and during the stop is available when it exists.

Expert testimony on breathalyzer reliability, rising BAC, or the pharmacology of alcohol elimination is available where the scientific challenge is strong. The cross-examination of the officer on field sobriety test administration, observation period compliance, and breathalyzer protocol is thorough in every trial.

I have tried OUI cases in which the defendant had a BAC reading of .11, .13, and higher and secured not-guilty verdicts. The BAC number is the beginning of the analysis, not the end. A representative sample of trial results is available at Massachusetts Criminal Defense Trial Results.

OUI Trial Results: A Recent Representative Sample, 2025-26

• OUI Third Offense, Woburn District Court. Not guilty all counts.
• OUI, Concord District Court. Not guilty all counts.
• OUI, Third Offense, Lawrence District Court. Not guilty all counts.
• OUI, Second Offense, Waltham District Court. Not guilty all counts.

For the complete list of trial results including Superior Court felony acquittals, see Massachusetts Criminal Defense Trial Results. Local guides to how OUI cases move through two of the busiest courts in the region are available at Woburn District Court OUI and Criminal Cases and Quincy District Court Criminal Cases.

When to Go to Trial and When Not To

Not every OUI case is a trial case. Cases with a constitutionally defective stop are resolved through a Motion to Suppress and dismissal. Cases with borderline BAC, favorable video, and a credible sobriety narrative are strong trial candidates. Cases with strong evidence of impairment, a high BAC, and no constitutional infirmity may be better resolved through negotiation for the best available disposition.

The decision to go to trial is made with the defendant after a full review of all available evidence. It is never made on the basis of the BAC number alone. A CWOF with the alternative disposition under M.G.L. c. 90, § 24D is the most common resolution for first offenders. The 24D program carries probation for up to two years, a driver alcohol education program, and a license suspension of 45 to 90 days, with a 210-day suspension for drivers under 21. That disposition still carries significant collateral consequences for licensed professionals, non-citizens, CDL holders, and federal employees that make a not-guilty verdict the only acceptable outcome in many cases. The immigration exposure is detailed at OUI Immigration Consequences in Massachusetts. See Massachusetts OUI FAQs.

Key Takeaways

• The prosecution must prove every element of an OUI charge, operation, a public way, and impairment or a .08 BAC, beyond a reasonable doubt. A breathalyzer reading does not establish guilt.
• An unconstitutional traffic stop renders all resulting evidence suppressible through a Motion to Suppress. See Illegal Searches and Seizures in Massachusetts.
• Field sobriety tests must be administered in strict compliance with NHTSA protocols. Deviations are grounds for exclusion or cross-examination, and the SJC’s Gerhardt and Canty decisions strictly limit what opinions the officer may offer the jury.
• The Draeger Alcotest 9510 result is subject to challenge on the 15-minute observation period, calibration records, the 0.02 consistency requirement, medical conditions, and the rising BAC phenomenon. See Why a Failed Breathalyzer Does Not Equal an OUI Conviction.
• Booking room video, dash camera footage, and witness testimony can directly contradict the prosecution’s impairment narrative at trial.
• A CWOF carries collateral consequences for licensed professionals, non-citizens, and CDL holders that are nearly identical to a conviction. The trial outcome is the only acceptable resolution in many cases.

I represent defendants in OUI cases across the Massachusetts District Courts and Boston Municipal Court. I am 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 me at 617.936.0201 for a free consultation. My Boston office is at 20 Park Plaza #400A, and my Quincy office is at 500 Victory Rd., Suite 400A. Available 24 hours a day.

Related Resources

• OUI Defense in Massachusetts, Main Practice Area Page
• Massachusetts OUI FAQs
• Massachusetts OUI License Suspensions
• Should I Take the Breathalyzer in Massachusetts?
• Why a Failed Breathalyzer Does Not Equal an OUI Conviction
• 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
• Waltham District Court