Breathalyzer vs. Blood Alcohol Testing: Accuracy, Convenience, and Legal Context

Comparing BAC Measurement Methods

Blood Testing (Gold Standard)

• Accuracy: Direct measurement of blood ethanol concentration; minimal interference.
• Invasiveness: Requires venipuncture; trained personnel; medical setting.
• Turnaround: Minutes to hours (lab processing).
• Legal weight: Generally preferred for evidentiary use in court.

Breathalyzer (Evidential Breath Testing)

• Principle: Infrared spectroscopy or fuel-cell oxidation of alveolar air; converts to estimated BAC via partition ratio (2100:1).
• Convenience: Portable, non-invasive, immediate results; roadside use.
• Accuracy: Highly reliable when calibrated/maintained; subject to physiological variables (breath temperature, hematocrit, mouth alcohol).
• Legal status: Accepted for screening and evidentiary purposes in most jurisdictions if device is approved and protocol followed.

Key Takeaway

Blood tests remain the reference standard for accuracy. Breathalyzers offer practical advantages for law enforcement screening and immediate decision-making. Neither is universally "more accurate"; context determines appropriateness.