Breath Test and Blood Alcohol Science in Massachusetts: The Alcotest 9510, the Regulations, and the Blood Rules

A Massachusetts OUI prosecution that includes a reported blood alcohol percentage depends on chemistry, physiology, a regulated instrument, and the operator’s compliance with the governing requirements. Before a jury may consider the number, the Commonwealth must establish the required foundation. The defendant may challenge the instrument, procedure, timing, or sample.

The discussion below addresses how the Alcotest 9510 measures alcohol, what the test sequence requires, how alcohol moves through the body, why timing matters, and how courts treat blood results. The companion page on Massachusetts breathalyzer defense addresses litigation using this science. The firm’s OUI and DUI defense page addresses the elements and consequences of the offense.

The Legal Framework for BAC Evidence in Massachusetts

Under G.L. c. 90, § 24(1)(a)(1), the Commonwealth may allege that the defendant operated with a blood alcohol percentage of .08 or greater or that the defendant operated while under the influence of intoxicating liquor. The Commonwealth may offer a breath or blood test as evidence under G.L. c. 90, § 24(1)(e). Breath testing is the more common procedure.

G.L. c. 90, § 24K requires a certified operator and a certified infrared breath-testing device. It also requires regulations governing testing methods, operator training and certification, and periodic device certification. Those requirements appear in 501 CMR 2.00. A deviation can support an admissibility challenge or cross-examination, but the remedy depends on the governing requirement, the Commonwealth’s foundation, and the facts of the test.

How the Alcotest 9510 Measures Breath Alcohol

The device used in Massachusetts is the Draeger Alcotest 9510. It is a dual-sensor instrument: it measures the same breath sample two different ways, by infrared absorption and by an electrochemical fuel cell, and it compares the results. The Supreme Judicial Court described the technology in detail in Commonwealth v. Camblin, 471 Mass. 639 (2015), a case about the Alcotest’s predecessor, and the principles carry forward to the 9510.

Infrared Absorption

The infrared measurement rests on a principle of physical chemistry: molecules absorb electromagnetic radiation, and only radiation of certain wavelengths will be absorbed by a molecule of a given compound. The device shines infrared light through the breath sample chamber. Ethanol molecules in the sample absorb part of that light, so less light reaches the detector than the source emitted, and the device computes the alcohol concentration from the difference. When a valid test occurs in Massachusetts, the infrared reading, not the fuel cell reading, is the measurement used to report the result. Camblin, 471 Mass. 639.

The Electrochemical Fuel Cell

The second sensor is an electrochemical fuel cell. Electrodes in the cell oxidize the alcohol in the breath sample, and the oxidation creates an electric current. The current is proportional to the alcohol content of the sample, and the cell’s sensors measure it. The fuel cell serves as a check on the infrared measurement rather than as the reported result.

The Tight Agreement Requirement

For the device to produce a result, the infrared and fuel cell readings must be in tight agreement with one another. If the two readings do not agree, the test aborts. The manufacturer’s position, described in the Camblin record, is that the two technologies together make the instrument specific to ethanol even though neither sensor alone is: an interfering substance that affects the two sensors differently produces disagreement, and disagreement ends the test. Whether the design accomplishes that in every case was contested by the defense experts in Camblin, and that contest is discussed below.

The Regulated Test Sequence Under 501 CMR 2.00

Under 501 CMR 2.00, the operator follows a prescribed sequence. The instrument and operator generate records that the defense may request and review.

The 15-Minute Observation Period

Under 501 CMR 2.13, the breath test operator must observe the person for at least 15 minutes immediately before the test. If the operator has reason to believe that the person brought a substance into the mouth during that period, the operator must restart the observation. An alleged mouth event is not automatically a required restart, and a deviation does not automatically require exclusion.

The Commonwealth must establish the required foundation. Booking video, cruiser video, reports, and the test record may show what the operator observed and whether the prescribed period occurred. Under Commonwealth v. Pierre, 72 Mass. App. Ct. 230, 234 to 235 (2008), the court separately analyzes the regulatory requirement, evidentiary foundation, and requested remedy.

The Two Breath Samples and the Control Standard

Under 501 CMR 2.14, a valid breath test sequence consists of one adequate breath sample analysis, one control-standard analysis, and a second adequate breath sample analysis. The two breath samples must agree within plus or minus .02 blood alcohol content units. If they do not, the operator must begin a new sequence. The control standard is a sample of known alcohol concentration used to test device performance during the sequence.

A certified operator must administer the sequence on a certified device. The printed test record, control-standard lot records, and the device’s calibration and certification history permit review of those requirements.

Certification of the Device and the Operator

The Office of Alcohol Testing (OAT) periodically certifies devices, maintains calibration records, and trains and certifies operators under Section 24K. Courts examined OAT’s annual certification practices in the consolidated Ananias litigation described below.

How Alcohol Moves Through the Body

Consumed alcohol passes from the stomach and intestines into the blood, and a person’s blood alcohol level changes over time through absorption and elimination. Commonwealth v. Colturi, 448 Mass. 809 (2007). Alcohol consumed shortly before driving may still be absorbed during the drive and after it ends.

A blood alcohol level changes rather than remaining constant. A test measures the level at the time of the test, while the criminal charge concerns operation. The timing evidence therefore affects how strongly the later result supports an inference about the blood alcohol percentage during operation.

Rising Blood Alcohol and the Time-of-Operation Problem

The gap between the time of driving and the time of testing is the rising blood alcohol problem. Because absorption continues after the last drink, a driver’s blood alcohol level can be higher at the station than it was behind the wheel, a possibility the case law has long acknowledged. Estimating the level at the time of operation from a later test is called retrograde extrapolation, a calculation that works backward from the test result using rates of absorption and elimination. Colturi, 448 Mass. 809 n.2.

In Colturi, the Supreme Judicial Court held that the Commonwealth need not present expert retrograde-extrapolation testimony as a condition of admitting a breath result when the test occurred within a reasonable time after operation. Delay ordinarily concerns the weight of the evidence rather than admissibility. See also Commonwealth v. Marley, 396 Mass. 433, 438 to 439 (1985).

The timing question nevertheless remains available at trial. The greater the interval between operation and testing, the more closely the parties may examine drinking history, food, absorption, elimination, and the basis for connecting the station result to the time of operation.

Mouth Alcohol and Interfering Substances

The breath test assumes that the sample comes from deep lung air, where alcohol concentration tracks blood concentration. Alcohol in the mouth itself, from a recent drink, a regurgitation, or anything else that puts alcohol into the oral cavity, defeats that assumption, which is why the regulations impose the 15-minute observation period and why the device aborts a sequence when it reports mouth alcohol. 501 CMR 2.13.

Interfering substances present a separate question. In the Camblin litigation, defense experts identified compounds that absorb infrared radiation in the region examined by the device and disputed whether either sensor standing alone was specific to ethanol. The manufacturer relied on the dual-sensor design: the technologies respond differently to interferents, the readings must agree, and disagreement aborts the test.

The Supreme Judicial Court required a reliability hearing because the initial record on ethanol specificity was inadequate. Commonwealth v. Camblin, 471 Mass. 639 (2015). After that hearing, the Court upheld the finding that the device was reliable. Commonwealth v. Camblin, 478 Mass. 469 (2017). A defendant may nevertheless raise an adequately supported scientific reliability challenge under the Daubert-Lanigan standard.

The Office of Alcohol Testing, Ananias, and Hallinan

In the consolidated Ananias litigation, a District Court judge found that the Office of Alcohol Testing had no written protocols for annual calibration and certification of the Alcotest 9510 until September 15, 2014. The judge treated results from devices calibrated and certified between June 1, 2011 and September 14, 2014 as presumptively unreliable.

The litigation later established that OAT had withheld failed calibration worksheets from the defense. The resulting resolution required notice to approximately 27,000 affected defendants and imposed a judicially supervised exclusion period that ended on April 18, 2019.

In Commonwealth v. Hallinan, 491 Mass. 730 (2023), the Supreme Judicial Court addressed a motion to withdraw a guilty plea or obtain a new trial when the Commonwealth had used an affected Alcotest 9510 result against the defendant. For a qualifying result from the exclusion period, the defendant receives a conclusive presumption of egregious government misconduct. The defendant must still establish a reasonable probability that knowledge of the misconduct would have affected the decision to plead guilty.

The firm’s post on the exclusion era from Ananias to Hallinan addresses the history, affected results, and remaining prejudice requirement.

Blood Tests: Consent, Warrants, and Hospital Records

The Supreme Judicial Court has interpreted the consent requirement for blood evidence in three recent decisions. Under G.L. c. 90, § 24(1)(e), police may not substitute a search warrant for the defendant’s actual consent to a police-directed chemical analysis of blood in an ordinary OUI prosecution. Commonwealth v. Bohigian, 486 Mass. 209 (2020).

The same consent requirement applied when hospital staff originally drew the blood for treatment but the State Police crime laboratory later performed a chemical analysis at police direction. The Supreme Judicial Court suppressed that analysis in Commonwealth v. Moreau, 490 Mass. 387 (2022).

In Commonwealth v. Gannett, 496 Mass. 97 (2025), the Court held that mathematically converting a treatment-related hospital serum or plasma result into a whole-blood alcohol percentage was not a police chemical analysis requiring Section 24 consent. The Court did not hold that every converted number is automatically admissible. The Commonwealth still must satisfy the applicable medical-record, expert-opinion, and evidentiary-foundation requirements.

Hospitals commonly test serum or plasma rather than whole blood and may report the result in milligrams per deciliter. Serum and plasma values differ from whole-blood values, which is why a conversion may be offered before the number is expressed as a whole-blood alcohol percentage. A defense review identifies what was tested, who ordered and performed the test, the purpose of the draw, the consent record, the medical-record foundation, and the method and assumptions used in any conversion.

Refusals: Inadmissible at Trial, Consequential at the Registry

Under article 12 of the Massachusetts Declaration of Rights, a defendant’s refusal to take the breath test is generally inadmissible as evidence of guilt. Commonwealth v. McGrail, 419 Mass. 774 (1995). If the defense creates a misleading impression that the defendant cooperated fully or that police never offered a test, however, the judge may permit limited refusal evidence to rebut that impression. Statements or conduct during an attempted test require a separate analysis.

A refusal also produces Registry of Motor Vehicles consequences. The firm sets out the refusal periods, prior-record rules, consecutivity requirements, and Section 24D exception in its license-suspension guide. The separate guide on whether to take or refuse the police-station breath test addresses the immediate decision after an alcohol OUI arrest.

What the Science Means for the Defense

A defense review begins with the device records: OAT calibration and certification records, the operator’s certification, the printed sequence, the control-standard result, and the two-sample agreement. Booking video, cruiser video, and reports may establish whether the operator completed the observation period and the prescribed sequence.

The review then addresses timing and scientific foundation. Under Colturi, courts ordinarily treat testing delay as a question of evidentiary weight. Under Camblin, a defendant may raise an adequately supported challenge to instrument reliability. The firm applies the same evidence review in sobriety-checkpoint cases. Its breath-test and BAC FAQs provide shorter answers to common evidence questions.

A conviction or continuance without a finding may also raise separate issues for college and university students, licensed professionals, and noncitizens. The governing school, licensing, and immigration rules require independent analysis.

Who Attorney Serpa Represents

Attorney Serpa represents drivers in Greater Boston whose cases involve breath or blood evidence, including hospital draws after collisions and prior dispositions involving an affected Alcotest 9510 result. He handles the criminal case and advises clients about related Registry proceedings. Call 617.936.0201 for a confidential consultation.

Massachusetts Courts Where Attorney Serpa Tries These Cases

The court with jurisdiction over the alleged offense hears the OUI case. Attorney Serpa represents defendants in the Boston Municipal Court and the District Courts of eastern Massachusetts.

Related Serpa Law Office Resources

Related resources address field sobriety evidence, common Massachusetts OUI questions, and recording during a sobriety checkpoint under Commonwealth v. Grimaldi. The profile of Attorney Joe Serpa describes the firm’s trial practice.