Breath-Test Records Needed for Scientific Review

THE OKOROCHA FIRM * September 3, 2026 Expert Witness, Forensic Toxicology, Science

Published by THE OKOROCHA FIRM *. Read the full Content Disclaimer.

An evidential breath-test printout is a result summary, not the complete scientific record. Meaningful review requires the documents and data that show what the instrument measured, how the accepted samples were obtained, whether the instrument was operating within its quality requirements, and how the reported number was produced.

The exact records available depend on the jurisdiction, agency, device model, retention policy, and issues in the matter. This guide identifies scientific record categories, not a universal discovery demand or a statement that every item exists in every case.

Start with the complete subject-test sequence

The first request should capture the entire event, not only the final ticket. That includes each subject sample, blank, control, diagnostic, reference check, error, interruption, refusal entry, aborted attempt, and operator message. Exact timestamps matter because sequence order, observation time, repeated results, and delays can affect the scientific questions.

Where the instrument retains more detail than it prints, the native electronic record, audit trail, and exported data should be preserved. A reformatted report may omit flow, volume, duration, slope, plateau, detector, interferent, status, or error information recorded by the instrument.

Identify the instrument and the configuration actually used

A case record should identify the manufacturer, model, serial number, location, software or firmware version, configuration, and analytical technology. The operative user manual, technical manual, software release notes, and agency procedure help explain what each result field and acceptance code means.

The National Highway Traffic Safety Administration maintains model specifications and conforming-products lists for evidential breath alcohol measurement devices. NHTSA explains that its specifications establish performance criteria for device-model conformance testing. Inclusion of a model on a conforming-products list is relevant, but it does not by itself establish the condition, maintenance, calibration, or operation of the particular instrument used in an individual test.

See NHTSA’s Alcohol Measurement Devices and Calibration Units and the agency’s Model Specifications for Evidential Breath Alcohol Measurement Devices.

Calibration and reference-material records establish the measurement relationship

Calibration relates instrument response to reference values. Accuracy checks, calibration verifications, and control tests may evaluate whether performance remains within defined limits. These events should not be treated as interchangeable without reading the applicable procedure.

Useful records include calibration dates and results, acceptance limits, failed or repeated checks, corrective actions, reference-material certificates, lot numbers, assigned concentrations, uncertainty statements, expiration dates, preparation records, storage conditions, and metrological traceability. For dry-gas systems, cylinder pressure, temperature or pressure corrections, regulator information, and certificate data may matter. For wet-bath systems, solution preparation or certification, simulator identification, temperature records, and equilibration procedures may matter.

NIST defines a breath alcohol program as the policies, procedures, responsibilities, and resources necessary for core activities, including reference-material requirements, operator training, instrument maintenance and calibration, the evidential test sequence, and record retention. That program-level perspective is why a single passing check should not be reviewed in isolation from the governing quality system.

See the NIST definition of Breath Alcohol Program and ANSI/ASB Standard 055-24 listed in the NIST OSAC Standards Library.

Maintenance history can explain a result or an unexplained gap

Maintenance, repair, inspection, diagnostic, service, and out-of-service records show the instrument’s operational history. Review should include the period before and after the subject test, not an arbitrary single day. The relevant interval depends on the calibration schedule, failure history, issue presented, and retention system.

Look for recurring error codes, component replacement, detector or sensor work, software changes, failed quality checks, unexplained downtime, return-to-service decisions, and whether a repair required recalibration. The identity, training, and authority of the person performing the work may also be relevant under the program procedure.

The breath sample is part of the measurement

An instrument analyzes ethanol in an expired breath sample; it does not directly analyze blood. Mason and Dubowski reviewed instrumentation, physiology, and the uncertainties involved in converting a breath quantity into a presumed whole-blood concentration. Their work emphasized defining and reporting the breath measurement rather than obscuring it through an assumed personal blood conversion.

Dubowski’s controlled biological-factor study measured variation in end-expiratory temperature, available expired volume, carbon dioxide, and other sampling conditions. The findings illustrate why the accepted sample cannot be evaluated only from the final number. When recorded, sample volume, flow, duration, slope or plateau information, temperature, and rejection criteria help show whether the instrument accepted the intended portion of expiration.

See Mason and Dubowski, Breath-Alcohol Analysis: Uses, Methods, and Some Forensic Problems (1976) and Dubowski, Studies in Breath-Alcohol Analysis: Biological Factors (1975).

Observation and operator records must be tied to time

Obtain the procedure that governed pretest observation or deprivation, the operator’s contemporaneous documentation, video when available, and an exact timeline. The reviewer should identify the purpose of the procedure and determine whether the record documents compliance rather than assuming it from a checked box.

Operator training, certification, recertification, competency, and device-specific authorization records may help determine whether the person understood the instrument messages and followed the operative procedure. These records should be evaluated against the version of the procedure in effect on the test date.

Repeated results answer only part of the question

Two results within a program’s agreement tolerance can support repeatability during that test sequence. They do not independently prove the correctness of the reference value, eliminate a shared calibration bias, or show that every procedural and sampling requirement was met. A disagreement between results requires investigation rather than automatic selection of one number.

The reporting unit, rounding or truncation rule, decision threshold, uncertainty policy, and any automatic averaging or result-selection logic should be obtained. The underlying unrounded values may matter when the printed ticket displays fewer digits than the stored record.

Practical scientific record checklist

complete ticket, test sequence, native data, audit trail, error messages, and aborted attempts;
instrument model, serial number, software or firmware, configuration, manuals, and operative procedure;
calibration, verification, control, diagnostic, maintenance, repair, inspection, and out-of-service history;
reference-material certificates, lots, assigned values, uncertainty, traceability, expiration, preparation, and storage;
operator training, certification, competency, and device-specific authorization;
observation documentation, body-camera or facility video, dispatch records, and complete timeline;
sample volume, flow, duration, slope, plateau, detector, interferent, blank, and environmental data when recorded;
reporting units, unrounded values, agreement criteria, rounding or truncation rules, and uncertainty policy; and
alternative specimens, medical records, drinking history, and other case facts relevant to the scientific question.

The careful conclusion

A scientifically reviewable breath test is more than a displayed number. The complete record connects the accepted breath samples to the instrument, reference materials, calibration system, maintenance history, operator, procedure, software, timestamps, and reporting rules. Missing records do not automatically prove an unreliable result, but they can limit which propositions can be independently checked.

The sound approach is to define the question, request the records that bear on it, and distinguish device-model conformance from instrument-specific performance. This page provides educational scientific information and is not legal advice.

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