OUI / DUI Drunk Driving Defense Lawyer in Greater Boston

Massachusetts prosecutes drunk driving under G. L. c. 90, § 24, the operating under the influence statute. The charge is commonly called OUI, and it carries two consequences that move at the same time: a criminal case in the District Court or the Boston Municipal Court, and a license suspension at the Registry of Motor Vehicles. Attorney Serpa has tried these cases in the Greater Boston courts for thirty years. This page explains what the Commonwealth must prove, how the breath test and the field sobriety tests work, what a conviction and a refusal cost, and how the defense is built.

The statute states a single offense that the Commonwealth may prove in either of two ways. Under G. L. c. 90, § 24(1)(a)(1), a person is guilty who operates a motor vehicle, on a way or in a place where the public has access, either while under the influence of intoxicating liquor or with a blood alcohol percentage of .08 or greater. The first way is the impairment theory. The second is the per se theory, and it requires no proof of impaired driving, only the test result. The model instruction that a judge reads to the jury explains that these are two ways of committing one crime. Massachusetts District Court Criminal Model Jury Instruction 5.310, “Operating Under the Influence of Intoxicating Liquor” (rev. Mar. 2023).

The Elements the Commonwealth Must Prove

The Commonwealth must prove three elements beyond a reasonable doubt: operation, a public way, and either impairment or a blood alcohol level of .08 or greater. Each element must be proved, and each is open to challenge.

Operation is defined broadly. A person operates a motor vehicle by intentionally doing something that could set the vehicle in motion, whether by itself or as one step toward it. Commonwealth v. Uski, 263 Mass. 22 (1928). The vehicle does not have to move, and the engine does not have to be running. Commonwealth v. Ginnetti, 400 Mass. 181 (1987). The Supreme Judicial Court confirmed how far this extends in Commonwealth v. Wurtzberger, 496 Mass. 203 (2025), where an impaired person sat in the driver’s seat with the key turned far enough to power the radio and the engine off. The court held that the evidence was enough to prove operation, because turning the key to power the vehicle’s electrical system is an act that could contribute to setting the vehicle in motion. Operation is often the contested element when the police find a driver parked, stopped on the shoulder, or asleep behind the wheel, and the defense examines whether the evidence shows an intentional act to engage the vehicle and whether another person may have driven.

The public way element requires that the operation occur, in the words of the statute, upon a way or in a place to which the public has a right of access, or to which members of the public have access as invitees or licensees. G. L. c. 90, § 24(1)(a)(1). The word “way” is defined in G. L. c. 90, § 1. The statute reaches only a place the public may reach by motor vehicle, and it is the status of the place, not the status of the driver, that controls. Commonwealth v. George, 406 Mass. 635 (1990). A place shows public access through objective indicia such as paving, curbing, street lights, traffic signals, and abutting homes or businesses. Commonwealth v. Smithson, 41 Mass. App. Ct. 545 (1996). Whether a place is one of public access is a legal conclusion that an appellate court reviews on the objective circumstances. Commonwealth v. Virgilio, 79 Mass. App. Ct. 570 (2011). A parcel posted against trespassers and used without the owner’s permission is not such a place. Commonwealth v. Callahan, 405 Mass. 200 (1989). A private lot behind a locked gate is a different matter, and the element is not automatic.

The third element is proved in one of two ways. On the impairment theory, the Commonwealth relies on observational evidence that the person’s consumption of alcohol impaired the ability to operate a motor vehicle safely. Commonwealth v. Connolly, 394 Mass. 169 (1985). It does not have to prove erratic driving, only a diminished capacity to drive safely. On the per se theory, the Commonwealth relies on a test result at or above .08 percent, whether from a certified breath test or from a hospital record of the blood alcohol level, and it does not have to prove impairment at all. Commonwealth v. Colturi, 448 Mass. 809 (2007). For a driver 21 or older the threshold is .08 percent, and for a driver under 21 it is .02 percent.

The Breath Test

The breath test used in Massachusetts is the Draeger Alcotest 9510. A breath result is not valid unless it was produced by a certified operator, meaning a police officer or State Trooper certified each year to administer the test, on an approved infrared device, using methods approved by the Secretary of Public Safety. G. L. c. 90, § 24K. The statute requires a fixed sequence: an adequate breath sample, a calibration standard analysis, and a second adequate breath sample. The Office of Alcohol Testing certifies the devices and sets the standards under the breath test regulations. 501 CMR 2.00. Each device must be certified, and a certification is valid for one year. The calibration standard in a valid test must read between 0.074 and 0.086. A missing annual certification, a bad calibration record, or a broken sequence is a foundation problem, and it can keep the result out. The firm explains the instrument and the science in detail on its pages on the breath test and the Alcotest 9510 and on defending the breath test.

The reliability of the Alcotest 9510 was litigated across the Commonwealth in Commonwealth v. Ananias, No. 1248 CR 1075 (Mass. Dist. Ct. July 29, 2019). The court excluded breath results from machines used between June 2011 and April 18, 2019, because the Office of Alcohol Testing had withheld records showing reliability problems with the machines. Breath results are admissible again for machines certified on or after April 18, 2019, subject to a case by case challenge to the reliability of the particular machine. The result on a given case still depends on whether the Commonwealth can produce the certification and calibration records for the specific machine on the specific day.

The Breath Test Refusal

A driver may refuse the breath test, and the refusal carries an automatic license suspension that the Registry imposes at once, separate from and in addition to any suspension on conviction. G. L. c. 90, § 24(1)(f)(1). The refusal suspension is 180 days for a driver 21 or older with no prior offense, three years for a driver under 21 or a driver with one prior offense, and five years for a driver with two prior offenses. A refusal after a prior conviction for operating under the influence causing serious injury carries a 10 year loss, and a refusal after a prior conviction for motor vehicle homicide carries a lifetime loss. These are Registry consequences, and they run whether or not the criminal case results in a conviction.

A refusal is not admissible against the driver at trial. The statute provides that evidence of a refusal is not admissible in a civil or criminal proceeding. G. L. c. 90, § 24(1)(e). The rule also has a constitutional basis. A statute that made breath test refusal admissible in a criminal case would violate article 12 of the Massachusetts Declaration of Rights, because a refusal is testimonial. Opinion of the Justices, 412 Mass. 1201 (1992). The same protection covers a refusal to perform field sobriety tests, because a Massachusetts driver has no obligation to perform them. Commonwealth v. McGrail, 419 Mass. 774 (1995). On this point Massachusetts protects a driver more than the Fifth Amendment does. The breath test refusal and license suspension page explains the Registry side in full.

The Field Sobriety Tests

The standardized field sobriety tests are the horizontal gaze nystagmus test, the walk and turn, and the one leg stand. The National Highway Traffic Safety Administration designed them to classify a driver’s blood alcohol at or above .08, at the accuracy rates the agency claims for them. The walk and turn is scored on two or more of eight clues, the one leg stand on two or more of four clues, and the horizontal gaze nystagmus test on four or more of six clues. The manual does not contain a failing score. The word “failed” is courtroom shorthand, not a result the test produces, and an officer should not testify that a driver passed or failed.

The horizontal gaze nystagmus test is different from the other two. It rests on a scientific proposition about involuntary eye movement, so it requires expert testimony and a scientific foundation before a jury may hear it. Commonwealth v. Sands, 424 Mass. 184 (1997). The walk and turn and the one leg stand are within a juror’s common experience and do not require an expert. An officer who watched the driver may give an opinion on the driver’s level of sobriety, but may not give an opinion on the ultimate question, whether the driver was under the influence or whether alcohol impaired the ability to operate. Commonwealth v. Canty, 466 Mass. 535 (2013). The firm cross-examines the officer on the instructions given, the conditions of the roadside, and the scoring on its page on cross-examining the field sobriety opinion, and it explains the tests and the science on its field sobriety test defense page.

Operating Under the Influence of Drugs

Operating under the influence of drugs is also a crime under G. L. c. 90, § 24, but the proof is different. The field sobriety tests are supported scientifically for alcohol only, not for marijuana or other drugs, and there is no scientific consensus that they show impairment by marijuana, so they are not admissible as proof of drug impairment. In a marijuana case the tests may be admitted only as roadside assessments of balance and coordination that a layman may interpret, and an officer may not testify that the driver passed or failed or give a lay opinion that the driver was high. Commonwealth v. Gerhardt, 477 Mass. 775 (2017). The firm addresses drug cases on its OUI drugs and marijuana defense page.

The Two Proceedings: The Criminal Case and the Registry

An OUI arrest starts two separate proceedings. The criminal case runs in the District Court or the Boston Municipal Court, where the question is guilt. The license case runs at the Registry of Motor Vehicles, where the question is suspension of one’s driver’s license. The two are governed by different rules, and each proceeds separately. A refusal suspension takes effect at the station when the driver is arrested. A first offender who instead takes the test and registers .08 or greater has the license taken by the police at the station, a suspension of up to 30 days that runs until the case is resolved. G. L. c. 90, § 24(1)(f). A suspension on conviction is separate again. Attorney Serpa handles the criminal case and advises on the Registry process, and he does not appear with clients at the Registry. The firm explains the license side on its pages on OUI license suspensions and the hardship license.

Penalties by Offense Number

A first offense under G. L. c. 90, § 24(1)(a)(1) is punishable by a fine of not less than $500 and not more than $5,000, by incarceration of up to two and one half years in a house of correction, or by both, along with a mandatory $250 head injury assessment and a $50 assessment. A conviction revokes the license for one year, with a work or education hardship license available after three months.

Most first offenders resolve the case under the alternative disposition in G. L. c. 90, § 24D. A person is eligible as a true first offender, and once in a lifetime a person is eligible whose single prior like offense was disposed of by a court of the Commonwealth or any other jurisdiction 10 years or more before the date of the new offense. The 24D disposition places the person on probation for up to two years, requires the Driver Alcohol Education program, and suspends the license for 45 to 90 days, with a hardship license available upon enrollment in the Driver Alcohol Education program. An ignition interlock device may be required if the blood alcohol level was .15 or greater. A person is not eligible if the incident caused serious injury or death.

A second offense is punishable by a fine of not less than $600 and not more than $10,000, by incarceration of not less than 60 days and not more than two and one half years in a house of correction, or by both, of which 30 days must be served. As an alternative to that jail time, a second offender who consents may instead be placed on probation for two years with a mandatory 14 day residential alcohol treatment program, on the judge’s written findings. G. L. c. 90, § 24(1)(a)(1). A second offense ordinarily revokes the license for two years. When the only prior is 10 years or more old, the person may receive the first offender type disposition under G. L. c. 90, § 24D, which limits the license loss to 45 to 90 days rather than two years. Commonwealth v. Cahill, 442 Mass. 127 (2004). The firm explains this second chance on its Cahill second offense page.

The third and later offenses are felonies. A third offense is punishable by a fine of not less than $1,000 and not more than $15,000 and by two and one half to five years in state prison or not less than 180 days in a house of correction, of which 150 days must be served, and it revokes the license for eight years. A fourth offense is punishable by a fine of not less than $1,500 and not more than $25,000 and by two and one half to five years in state prison or two to two and one half years in a house of correction, of which one year must be served, and it revokes the license for ten years. A fifth offense is punishable by a fine of not less than $2,000 and not more than $50,000 and by two and one half to five years in state prison or two and one half years in a house of correction, of which two years must be served, and it revokes the license for life. Massachusetts counts prior offenses over the driver’s lifetime, so an old prior still counts, subject only to the narrow second chance described above. Commonwealth v. Richards, 480 Mass. 413 (2018).

Melanie’s Law requires an ignition interlock device for repeat offenders. G. L. c. 90, § 24½. A person whose license is suspended for an OUI conviction or program assignment, in the Commonwealth or any other jurisdiction, and who has a prior such conviction or assignment, cannot obtain a new or restored license unless a certified device is installed on every vehicle the person owns, leases, and operates, and the device must remain for two years. The device is also a mandatory condition of a hardship license for a second offender, which becomes available only after one year. Operating in violation of the device requirement is a separate crime. G. L. c. 90, § 24S.

A prior offense can come from another state. Under G. L. c. 90, § 24, a prior offense includes a conviction, or a court ordered program assignment, entered by a court of the Commonwealth or any other jurisdiction for a like violation. An out-of-state OUI conviction counts as a prior offense. An out-of-state action that was purely administrative, such as an implied consent refusal suspension entered by a motor vehicle agency with no court disposition, is neither a conviction nor a court assignment, and it does not count as a prior offense. Similarly, a Massachusetts OUI conviction or program can count as a prior offense if a driver is charged with a subsequent offense in another state.

Serious Injury, Death, and a Child in the Vehicle

A person charged with OUI that caused death or serious bodily injury faces enhanced sentences. An OUI with serious bodily injury and reckless or negligent operation is a felony under G. L. c. 90, § 24L. It is punishable by two and one half to ten years in state prison, or by six months to two and one half years in a house of correction, with a mandatory minimum of six months. The statute defines serious bodily injury as an injury that creates a substantial risk of death, or that causes total disability or the loss or substantial impairment of a bodily function for a substantial period of time. G. L. c. 90, § 24L. A conviction revokes the defendant’s driver’s license for two years.

Motor vehicle homicide while operating under the influence can be a misdemeanor or a felony under G. L. c. 90, § 24G. It is a felony if a driver operated recklessly or negligently and caused the death of another person. It is punishable by two and one half to fifteen years in state prison, or by one to two and one half years in a house of correction, with a mandatory minimum of one year. A conviction revokes a driver’s license for fifteen years on a first offense and for life on a subsequent offense. The offense is a misdemeanor where a person operating under the influence caused a death without separate proof of reckless operation, and it carries a house of correction term of 30 days to two and one half years.

Operating under the influence with a child 14 years old or younger in the vehicle is also an offense under G. L. c. 90, § 24V. It can be charged in addition to the underlying OUI. A first offense carries a fine of $1,000 to $5,000 and 90 days to two and one half years in a house of correction. A first offense also suspends a driver’s license for one year. Each of these charges must be proven with the same elements of operation, a public way, and impairment or a blood alcohol level of .08 or greater, and each adds a question of causation. The firm defends them alongside the underlying charge, and it addresses the related offenses of motor vehicle homicide and operating to endanger on its own page.

The Defense of a Massachusetts OUI Case

A strong defense begins at the stop. The police need a lawful reason to stop the vehicle, a lawful basis for an exit order, and a lawful basis for each step that follows. The defense examines the reason for the stop, the observations the officer recorded, the instructions given before the field sobriety tests, the conditions of the roadside, and the foundation for the breath test. Where the stop or a later step was unlawful, a motion to suppress can lead to dismissal, because a judge can suppress the officer’s observations and any other evidence the police obtained after a bad motor vehicle stop. A motion for a required finding of not guilty can end the case before jury deliberations if the Commonwealth has not proven one or more of the elements discussed above. At trial, cross-examination tests the officer’s observations, the field test scoring, and the breath test result, if applicable. Attorney Serpa conducts these examinations with deep preparation but without a script. The firm discusses his cross-examination skills on its cross-examination page.

An OUI complaint often includes additional offenses, usually operating to endanger, negligent or reckless operation, or operating after a suspension. Many OUI arrests also begin at a sobriety checkpoint, which has its own rules.

Who Attorney Serpa Represents

Attorney Serpa represents people charged with operating under the influence across Greater Boston, from a first offense to a subsequent offense, and in cases that involve a breath test, a refusal, drugs, or a serious injury. The office also represents those who face added consequences from an OUI, including college and university students, licensed professionals, and non-citizens. The office answers questions about the criminal case and the Registry consequences together, so a client understands both from the start. Contact Serpa Law Office at 617.936.0201 for a free, confidential consultation. Boston office: 20 Park Plaza, Suite 400A. Quincy office: 500 Victory Road, Suite 400A. Available 24 hours a day.

Massachusetts Courts Where Attorney Serpa Tries These Cases

Attorney Serpa tries OUI cases in the Boston Municipal Court and in the District Courts of Greater Boston, including the courts in Quincy, Dedham, Cambridge, Somerville, Malden, Framingham, and the surrounding communities. He has tried cases in these buildings for thirty years. The firm keeps a guide to the Massachusetts District Courts, and Attorney Serpa’s background is on his profile.

Related Serpa Law Office Resources

Readers of this page often turn next to the firm’s pages on the breath test and blood alcohol science, breath test evidence, the field sobriety tests, license suspensions, the hardship license, the Cahill second offense disposition, OUI drugs and marijuana, sobriety checkpoints, and the broader group of Massachusetts motor vehicle crimes. Common questions are answered on the Massachusetts OUI FAQs.

Last Reviewed: July 2026