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

After a Massachusetts OUI arrest, the breath test final analysis from a breathalyzer or the result of a blood alcohol test can become the central evidence in the criminal case. A breath or blood test measures alcohol in a particular sample at a particular time, while the charge concerns the person’s operation of a vehicle. The meaning, reliability, and admissibility of the test result depend on the instrument, the operator, the required procedure, the timing of the sample, and the way alcohol moves through the body.

This page explains how the Alcotest 9510 measures breath alcohol, what the regulated sequence requires, how mouth alcohol and testing time affect the breath test final analysis, and how Massachusetts courts treat police-directed blood analysis and hospital alcohol records. The companion page on Massachusetts breathalyzer defense addresses the records, motions, and trial objections used to litigate breath and blood alcohol evidence. The guide to taking the breath test or refusing the breathalyzer compares the immediate choices after an alcohol OUI arrest. The OUI defense page addresses the elements and consequences of the charge.

The Legal Framework for BAC Evidence in Massachusetts

Under M.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 M.G.L. c. 90, § 24(1)(e). Breath testing is the more common procedure.

M.G.L. c. 90, § 24K requires a certified operator and a certified infrared breath-testing device. Section 24K also requires regulations governing testing methods, operator training and certification, and periodic device certification. The breath-testing regulations appear in 501 CMR 2.00. A deviation from the regulations 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 breath-test device approved by the Office of Alcohol Testing for evidentiary use in Massachusetts is the Draeger Alcotest 9510. The current Massachusetts Breath Test Operator’s Manual and other official program materials describe the 9510 as a dual-sensor instrument. The 9510 analyzes each breath sample by infrared absorption and by an electrochemical fuel cell, then compares the measurements.

Commonwealth v. Camblin, 471 Mass. 639 (2015), and Commonwealth v. Camblin, 478 Mass. 469 (2017), concern the older Alcotest 7110 MK III-C, not the 9510. The Camblin decisions remain part of the Massachusetts framework for a scientific reliability challenge, but they do not establish that the breath test final analysis from a particular 9510 device is accurate or admissible.

Infrared Absorption

The infrared measurement is based on the principle of physical chemistry that a molecule of a given compound absorbs electromagnetic radiation only at certain wavelengths. The device shines infrared light through the breath sample chamber. Ethanol molecules in the sample absorb part of the infrared light, so less light reaches the detector than the source emitted. The device computes the alcohol concentration from the difference. Official Massachusetts program materials identify the infrared measurement, rather than the fuel-cell measurement, as the result used to report the alcohol concentration for each sample.

The Electrochemical Fuel Cell

The second sensor is an electrochemical fuel cell. Electrodes in the cell oxidize alcohol in the breath sample. The oxidation creates an electric current. The current changes with the alcohol content of the sample. The fuel cell serves as a separate check on the infrared measurement rather than as the reported result.

Sensor Agreement and Sample Agreement

The 9510 program materials explain that the device compares the infrared and fuel-cell measurements and does not complete the analysis when its internal requirements are not met. That internal sensor comparison is different from the regulation requiring the two separate breath samples to agree within plus or minus .020 blood alcohol content units. The internal sensor comparison checks the readings of two technologies on one sample. The two-sample agreement requirement applies to the reported results of the first and second samples in the regulated sequence.

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 administering the breath test. An operator who has reason to believe that the person introduced any item into the mouth must restart the observation period. The operator must end the sequence, restart the 15-minute observation period, and begin a new sequence if the instrument reports mouth alcohol during the test sequence.

The Commonwealth bears the burden of establishing compliance with the required observation procedure. Booking video, cruiser video, reports, and the test record may show what the operator observed and whether the prescribed period occurred. Minor weaknesses ordinarily affect the weight of the breath-test evidence, but a judge can exclude the breath test final analysis because of a substantial departure from the regulation. Commonwealth v. Pierre, 72 Mass. App. Ct. 230, 234 to 235 (2008).

The Two Breath Samples and the Control Standard

Under 501 CMR 2.14, the arresting officer or breath test operator must document the person’s consent to the breath test. A certified operator must administer the test on a certified device. The sequence consists of one adequate breath-sample analysis, one control-standard analysis, and a second adequate breath-sample analysis. The two breath samples must be within plus or minus 0.020 blood alcohol content units of each other.

The operator must begin a new sequence if the two breath samples are not within 0.020 blood alcohol content units of each other. 501 CMR 2.16 governs a test that ends before the second sample. 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 defense can check compliance with the sequence and certification requirements in the printed test record, control-standard lot records, and the device’s calibration and certification history.

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. 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 the degree to which 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. Courts have long recognized that absorption continues after the last drink, so a driver’s blood alcohol level can be higher at the time of testing than it was during operation. 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. at 816 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 test final analysis 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 defense may nevertheless raise the timing question 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 later result to the time of operation.

Mouth Alcohol and Interfering Substances

The breath test is based on the assumption that the sample comes from deep lung air, where alcohol concentration corresponds to blood concentration. Alcohol in the mouth itself, from a drink taken shortly before the test, a regurgitation, or anything else that puts alcohol into the oral cavity, means that the sample no longer comes only from deep lung air. Mouth alcohol is the reason the regulations impose the 15-minute observation period and the reason the device aborts a sequence when it reports mouth alcohol. 501 CMR 2.13.

Interfering substances present a separate question. Official 9510 training materials describe the fuel cell as a check for substances that can affect the infrared analysis. In a case-specific challenge, the defense asks whether the instrument identified an interferent, whether the sequence completed, and whether medical, environmental, or device evidence supplies a reliable basis to question the breath test final analysis.

In the first Camblin decision, the Supreme Judicial Court required a reliability hearing because the initial record on the predecessor Alcotest 7110’s ethanol specificity was inadequate. Camblin, 471 Mass. 639. After the reliability hearing, the Court upheld the finding that the 7110 technology was reliable. Camblin, 478 Mass. 469. The Camblin decisions establish that a defendant may bring an adequately supported scientific reliability challenge under the Daubert-Lanigan standard even when the breath test complied with the regulations. In Camblin, the Supreme Judicial Court did not decide every scientific question about the 9510 or every individual test.

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 breath test final analyses from devices calibrated and certified between June 1, 2011, and September 14, 2014, as presumptively unreliable.

The litigation later established that OAT had produced 1,976 calibration worksheets while intentionally withholding another 432 worksheets reporting failed calibration efforts. Later orders required notice to approximately 27,000 affected defendants and set the conditions under which the Commonwealth could use a breath test final analysis from an Alcotest 9510 device.

In Commonwealth v. Hallinan, 491 Mass. 730 (2023), the Supreme Judicial Court considered breath tests performed on an Alcotest 9510 device last calibrated and certified before April 18, 2019. The Court held that a defendant whose case included such a test receives a conclusive presumption of egregious government misconduct.

The application of Hallinan depends on the calibration and certification history of the device, not on the date on which the defendant submitted to the breath test. A defendant seeking to reopen a past disposition must still file and support the appropriate motion under Massachusetts Rule of Criminal Procedure 30. The judge must exclude an affected breath test final analysis from a current or future trial.

The complete guide to Commonwealth v. Hallinan and the Alcotest 9510 cases explains the history, the amended affected-device rule, the separate standards for pleas and trial convictions, and what happens if a Rule 30 motion is allowed.

Hallinan File-Review Checklist

The client should gather the court and docket number, the date and form of the disposition, any breath-test ticket or discovery still available, and the sentencing and license records. Counsel should verify that the instrument was an Alcotest 9510. Counsel should also verify the device serial number, the date on which that device was last calibrated and certified, how the breath test final analysis affected the disposition or trial, and which Rule 30 standard applies. Counsel cannot determine whether Hallinan applies from the date of the breath test alone.

Blood Tests: Consent, Warrants, and Hospital Records

The Supreme Judicial Court has interpreted the consent requirement for blood evidence in the four decisions discussed below. Under M.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).

M.G.L. c. 90, § 24(1)(e) still required the defendant’s consent where hospital personnel drew blood for medical treatment and police later directed the State Police crime laboratory to chemically analyze the physical sample. The Supreme Judicial Court held the resulting analysis inadmissible in the ordinary OUI prosecution. Commonwealth v. Moreau, 490 Mass. 387, 394 to 395 (2022). That statutory consent rule governs an ordinary OUI prosecution under M.G.L. c. 90, § 24(1)(a). The statutory consent rule does not govern the aggravated OUI offenses addressed in Commonwealth v. Zucchino, 493 Mass. 747, 751 (2024).

In Commonwealth v. Gannett, 496 Mass. 97, 103 to 105 (2025), the Supreme Judicial Court addressed the use of serum or plasma ethanol data already contained in medical records. The Court held that mathematically converting the data into a blood alcohol percentage is not a chemical analysis of a physical blood sample under M.G.L. c. 90, § 24(1)(e). The consent requirement therefore does not bar the conversion on that ground. The decision does not establish that every proposed conversion method is scientifically reliable or otherwise admissible. Medical-record foundation, expert qualification, methodology, and other evidentiary objections remain separate questions.

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. A party may therefore offer a conversion that expresses the hospital value as a whole-blood alcohol percentage. The defense 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.

Refusing the Breathalyzer: Trial and Registry Consequences

Under M.G.L. c. 90, § 24(1)(e) and Article 12 of the Massachusetts Declaration of Rights, a defendant’s refusal to take the breath test is generally inadmissible in the criminal trial. Opinion of the Justices, 412 Mass. 1201, 1208 to 1211 (1992); Commonwealth v. Zevitas, 418 Mass. 677, 683 (1994). The judge may not admit evidence that the defendant refused the breathalyzer merely because the trial evidence mentions that police offered it. Commonwealth v. Seymour, 39 Mass. App. Ct. 672, 677 (1996).

Refusal evidence is different from evidence of an attempted test after consent. An officer may testify about the defendant’s physical conduct during the attempts if the defendant consents to the breath test but does not provide an adequate sample. The Commonwealth must establish the required foundation, including a certified operator and a properly functioning instrument, before it may offer the failure to provide an adequate sample as evidence of impairment or consciousness of guilt. Commonwealth v. AdonSoto, 475 Mass. 497, 500 to 501 (2016); Commonwealth v. Daigle, 99 Mass. App. Ct. 107, 112 (2021).

The Registry of Motor Vehicles also suspends the license of a driver who refuses the breathalyzer. The firm sets out the suspension periods, prior-offense rules, consecutive-period requirement, and Section 24D limited-license provision in its license-suspension guide.

What the Science Means for the Defense

The defense begins its review with the 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 defense then reviews the timing of the test and the scientific foundation of the result. 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. The firm’s 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 earlier dispositions involving an affected breath test final analysis from an Alcotest 9510 device. Attorney Serpa 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.