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Potential Sources of Error in Blood Alcohol Testing

Quantitative Analysis of alcohol concentrations in a biological fluid is a process potentially subject to sources of error whether conducted in a forensic laboratory or in a police station. The use of breath testing equipment introduces an additional source of uncertainty because the device measures ethanol concentrations in breath and provides an estimate of blood alcohol concentrations based on the breath alcohol measurement. The assumptions in making that estimate are well documented in scientific literature. It is beyond the scope of this short article to provide an exhaustive list of known sources of error but rather to highlight several potential sources.

Contamination of the Breath Sample

- Gastro-Intestinal Reflux Disorder (GERD)
- Mouth Alcohol
- Inadequate or Invalid Observation period

Interfering Substances

- Compounds with Overlapping Infrared Spectra
- Diabetic Ketoacidosis
- Metronidazole

Pharmacokinetic Misinterpretations

- Rising ethanol Concentrations
- Inappropriate Reverse Extrapolation

Warning! Many of these potential sources of error will be downplayed by members of law enforcement. It is imperative to use these strategies you must consider hiring an expert witness to explain these to the jury.