## Challenging breath-test evidence in Tennessee DUI cases Breath-alcohol testing is presented as scientific + reliable, but breath-test machines have well-documented errors. Tennessee defendants can challenge results on multiple grounds — and successful challenges have led to mass dismissals across multiple states. ## How breath-test machines work **Common machines:** - **Intoxilyzer 8000 / 9000** (CMI Inc.) - **DataMaster** (National Patent Analytical) - **Alcotest 9510 / 7110** (Dräger) - **BAC Datamaster CDM** **Technology:** - Infrared spectroscopy (IR) - Fuel-cell technology - Or combination - Measures alcohol in breath - Calculates BAC via partition ratio (typically 2100:1) ## Constitutional challenges **Birchfield v. North Dakota (2016):** - Warrant required for blood test - Breath test = warrantless OK - Implied consent statutes restricted for blood - Important DUI law impact **Mitchell v. Wisconsin (2019):** - Unconscious DUI suspect — implied consent - Limited to specific circumstances ## Calibration challenges **Breath-test machines must be calibrated:** - Regular calibration required - Specific protocols - Documentation maintained - ${s.name}-specific intervals **Common calibration issues:** - Missed calibration - Failed calibration not addressed - Improper calibration procedures - Inadequate calibration records - Calibration done by uncertified person - Use of non-certified standards - Equipment moved without recalibration ## Maintenance challenges **Required maintenance:** - Software updates - Hardware checks - Cleaning procedures - Replacement of parts - Documentation logs **Common maintenance issues:** - Skipped scheduled maintenance - Inadequate maintenance records - Repairs not documented - Refurbishment without recalibration - Components replaced incorrectly ## Operator error challenges **Operator must follow specific protocols:** - 15-20 minute observation period (no eating, drinking, smoking, vomiting, regurgitation) - Two readings within specific tolerance - Proper subject preparation - Proper instrument operation - Specific procedural steps **Common operator errors:** - Inadequate observation period - Operator distracted - Subject ate/drank/smoked during observation - Subject vomited / regurgitated - Improper testing technique - Inadequate operator certification - Operator unfamiliar with machine ## Mouth alcohol challenges **Critical issue:** - Recently consumed alcohol left in mouth - Belching / regurgitation - Dental work / dentures - Mouthwash - Cold medicines - GERD / acid reflux - Diabetic ketoacidosis **Effect:** - Falsely elevated BAC reading - Sometimes 2-3x actual BAC - Significant defense potential ## Machine reliability challenges **Source code issues:** - Manufacturers often refuse to disclose source code - Trade secret claims - Defendants challenge - Some courts ordered disclosure - Cmiel v. Dräger (NJ Supreme Court 2018) — significant ruling **Known machine issues:** - Software bugs disclosed in source code reviews - Specific machine recalls / problems - Manufacturing defects - Calibration drift over time ## Margin of error **Inherent measurement error:** - Machine accuracy: typically ±0.005 BAC - Subject variability: significantly more - Borderline cases: critical - 0.08 BAC vs 0.10 BAC: huge difference legally ## Partition ratio challenges **Standard 2100:1 ratio:** - Assumes specific blood-to-breath relationship - Actual ratio varies 1:1300 to 1:3000 - Some individuals significantly different - Breath test overestimates for low ratio individuals ## Subject-specific factors **Affecting breath test accuracy:** - Body temperature (especially fevers) - Hyperventilation / hypoventilation - Medical conditions (asthma, COPD) - Diabetes (DKA mimics alcohol) - Recent illness - Diet / fasting - Specific medications - Personal hygiene products ## Procedural challenges **${s.name}-specific requirements:** - Specific arrest procedures - Specific testing procedures - Implied consent advisement - Right to independent test - Time of test (within hours of driving) - Specific operator certification - Specific observation period - Specific number of readings - Tolerance between readings **Failure to comply with state procedure** = often leads to suppression. ## Mass dismissals **Notable examples nationally:** - **New Jersey** (2019) — 13,000+ DUI dismissals after calibration issues - **Washington** (2017) — thousands dismissed - **Massachusetts** (2017) — 36,000 cases reviewed - **Pennsylvania** (multiple) — calibration issues - **Florida** (multiple) — Intoxilyzer 8000 source code issues **Pattern:** When calibration / source code / maintenance issues discovered, courts dismiss en masse. ## Discovery requests **Critical requests in DUI defense:** - Calibration records (specific time period) - Maintenance logs - Operator certification - Operator training records - Repair history - Software versions - Source code access - Standards used for calibration - Personnel who handled machine - Internal audits / inspections - Manufacturer correspondence ## Expert witnesses **Common DUI experts:** - Forensic toxicologists - Former state lab employees - Source code analysts - Calibration / metrology experts - Medical toxicologists **Cost: $2,500-$15,000+ typical** ## Independent testing rights **Most states allow:** - Right to independent blood test - At your expense - Specific procedures - Limited time after arrest - Critical right often forgotten **Independent test results:** - Can contradict breath test - Strong defense evidence - Time-sensitive ## Refusal to take breath test **${s.name} refusal consequences:** - Implied consent license suspension - Refusal admissible as evidence - Sometimes mandatory minimum penalties - Sometimes more severe than DUI conviction **Strategic decision:** - Often best to take the test - BUT consider personal circumstances - Don't make decision without counsel ## Strategic considerations **For DUI defense:** - Demand discovery on machine + procedures - Hire forensic expert if BAC borderline - Look for procedural violations - Consider mouth-alcohol issues - Examine medical conditions - Check officer certification - File motion to suppress if grounds - Pursue mass-dismissal opportunities **Settlement leverage:** - Strong technical challenge often leads to plea offers - Reduction to lesser charge - Diversion / DUI school - Sometimes outright dismissal ## Borderline cases — critical **0.08 vs 0.10 BAC:** - Major legal difference - Margin of error matters most - Calibration matters most - Procedural compliance critical - Worth investing in defense **0.15+ BAC:** - Aggravated DUI in many states - Enhanced penalties - Higher BAC machines may overestimate - Additional defenses helpful ## What you should do If charged with DUI in Tennessee based on breath test: hire experienced DUI attorney with technical knowledge. Demand all maintenance + calibration records. Consider expert review of testing procedures. Tennessee DUI specialists know local machines + protocols. Borderline BAC cases especially benefit from technical challenges. --- *This guide is general information about Tennessee DUI law as of mid-2026 and is not legal advice. Breath-test challenges are technical. Talk to a licensed Tennessee DUI attorney about your specific situation.*