Breath-alcohol analysis: uses, methods, and some forensic problems--review and opinion

Area of Science:

• Forensic Science
• Toxicology
• Analytical Chemistry

Background:

• Breath analysis is crucial for determining ethanol (alcohol) levels, particularly in forensic contexts.
• Existing methods for calculating whole blood ethanol concentration from breath samples present significant uncertainties.
• Physiological factors influencing ethanol elimination via breath are complex and contribute to measurement variability.

Purpose of the Study:

• To review the instrumentation and physiological factors in breath ethanol analysis for forensic applications.
• To highlight the inherent uncertainties in converting breath ethanol measurements to blood ethanol concentrations.
• To propose a shift in legal definitions for driving under the influence (DUI) offenses based on direct breath analysis.

Main Methods:

• Review of existing literature on breath analysis instrumentation for ethanol detection.
• Analysis of physiological factors affecting ethanol pharmacokinetics and breath excretion.
• Examination of the statistical and practical challenges in converting breath ethanol to blood ethanol values.

Main Results:

• Significant uncertainties exist when calculating blood ethanol concentration from breath samples.
• Current federal standards for evidential breath-testing devices may be insufficient for precise forensic use.
• The conversion of breath ethanol to blood ethanol for legal purposes is scientifically questionable.

Conclusions:

• Abandon the conversion of breath ethanol to blood ethanol concentration for forensic purposes.
• Statutorily define driving under the influence offenses based on direct breath ethanol measurements.
• Implement advanced breath-testing instruments exceeding current federal standards for accuracy and reliability.