The Need for Standardization of Exhaled Volume in Breath Alcohol Testing

Technical Note

Aaron Olson ✉️. DWI Journal. https://doi.org/10.61874/dwij/mgqj9294

Abstract

Inconsistent exhaled volume requirements across breath alcohol analyzers create a significant hurdle when comparing breath alcohol concentration (BrAC) from various analyzers. Vast differences in exhaled volume requirements among analyzers mean reliable BrAC comparisons cannot be made from one analyzer to another. Forensic scientists and manufacturers of breath alcohol analyzers must consider the ramifications of inconsistent exhaled volume requirements in the legal context for fair and reliable comparisons of BrAC to be made.

The Need For Standardization Of Exhaled Volume In Breath Alcohol Testing

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Introduction

Reliable measurements of BrAC are crucial in the legal context where a person's guilt or innocence and potential incarceration are at stake. However, determining an appropriate exhaled volume sampling requirement is more complex than it may seem (1–5). One challenge in defining the appropriate exhaled volume sampling requirement is that BrAC is heterogeneous and continues to rise throughout exhalation (6–8). 

Exhaled volume requirements amongst evidential breath alcohol analyzers vary widely. Vast differences in requirements mean that a subject could be under the legal BrAC limit for driving on one analyzer and simultaneously over the legal limit on another. 

For example, Figure 1 shows an expirogram of a subject who blew into the Minnesota version of the DataMaster DMT (DMT) (Intoximeters, St. Louis, MO). The expirogram shows what the subject’s BrAC would have been if tested with different evidential breath alcohol analyzers.

Figure 1. An expirogram from a subject blowing into the Minnesota DataMaster DMT.

Table 1 shows different outcomes based on various breath alcohol analyzers. In two analyzers, the subject would have been under the legal driving limit of 0.08 g/210L, while in one analyzer, the subject would have been over the legal limit. 

Table 1. Breath analyzer, jurisdiction, exhaled volume requirement, and BrAC for a subject under investigation for DWI.

Discussion

In breath alcohol testing, manufacturers have implemented minimum exhaled volume standards (usually 1.1 - 1.5 liters) but have paid little attention to the impact of the upper limit of exhaled volume. Without consistent standards for exhaled volume, situations will arise where a subject will be under the legal BrAC limit for driving on one analyzer while being over the legal limit on another. In the legal context, this raises questions about fairness based on the analyzer and exhaled volume parameters selected.

Conclusion

Breath alcohol analyzer manufacturers and forensic scientists must consider the impact of the maximum exhaled volume when comparing BrAC values. The lack of standardization of exhaled volume means that reliable BrAC comparisons cannot be made from one analyzer to the next.

Disclosures

The author serves as an expert witness in forensic toxicology cases.

References

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