[Blog editor’s note: Joshua Goldberg of Pittsburgh, PA writes into us to share information about Breath Alcohol Content machines.]

III. THE ACCURACY LIMITATIONS OF BREATH TESTING DEVICES

The courtroom must only permit sciences that accurately and reliably predict each defendant’s blood alcohol level. Yet, the twin assumptions of a 2100:1 partition ratio and a 34 ° C breath temperature dispel the evidential worthiness of breath testing.  However, assumptions are not breath testing’s only pitfalls.  The non-specificity of breath test machines, combined with a host of other accuracy limitations, likewise tarnishes breath testing’s scientific value.

Breath test devices such as the DataMaster and Intoxilyzer 5000 utilize infrared spectroscopy technology to detect and quantify the presence of alcohol in a breath sample.  This technology is ancient.  The National Highway Traffic Safety Association (NHTSA) publishes required breath test device specifications and conforming product lists.  See, 49 FR 48855 (1984).  While computer technology, over 30 years, evolved, breath testing remains inaccurate due to lack of specificity, or a failure to discriminate among interfering substances.

Lack of Specificity/ Interfering Substances

Both the Intoxilyzer 5000 and DataMaster breath testing devices utilize infrared technology to quantify alcohol in a breath sample.  The devices attempt to ascertain ethyl alcohol by its infrared footprint:

[E]thyl alcohol has a strong infrared absorption band in the 3.30 to 3.50 micron range utilized by most infrared breath alcohol testing instruments.  These instruments quantitate the amount of alcohol in the sample by measuring the infrared energy at specific wavelengths entering and emerging from the sample chamber.  The amount of infrared energy lost due to absorption is proportional to the alcohol concentration.

Patrick Harding, Methods for Breath Analysis, Medicolegal Aspects of Alcohol, 192 (James Garriott ed. 3rd ed. 1996).

In essence, breath testing devices use optic filters in an attempt to zero in on ethyl alcohol in breath to the exclusion of all other chemicals or compounds.   The optic filters (contained within the breath testing devices) supposedly enable the devices to “see” ethyl alcohol in a breath sample and ignore all other chemicals or compounds.

In practice, breath testing devices often fail to “see” a difference between ethyl alcohol and a myriad of other chemicals or compounds.  When a breath testing device fails to recognize the difference between ethyl alcohol and another chemical or compound, it creates two problems:  (1) the breath test device registers and quantifies a result for ethyl alcohol when there was no ethyl alcohol; or (2) the breath test device adds on the other chemical or compound to the ethyl alcohol detected and therefore produces a falsely inflated result.

“Interfering substances” give breath test devices difficulty distinguishing ethyl alcohol.   Documented interfering substances range from chemicals or compounds that occur naturally in the breath, to injected chemicals or compounds.  Interfering substances include:

●Alcohols (other than ethyl alcohol), esters, and certain ethers have been found to interfere at specific infrared wavelengths.

Reference: Dominick Labianca, Breath-alcohol analysis: a commentary on ethanol specificity in the 3- µm and 9-µm regions of the IR spectrum, in Forensic Toxicology Vol. 24, 92 (2006).

●Isopropanol, acetaldehyde, toluene, and methanol have all been found to be interfering substances in the Intoxilyzer 5000.

Reference: Variables Affecting the Accuracy and Precision of Breath Alcohol Instruments Including the Intoxilyzer 5000.  Stefan Rose and Kenneth Furton.

Interfering substances underscore chemicals produced naturally in the body (acetaldehyde) that create false positive or elevated BAC results.  The lungs, rather than the liver, produce Acetaldehyde  as a result of processing ethyl alcohol.  Taylor and Oberman, Drunk Driving Defense, § 7.02 at pp. at 540-41.  Further,  studies of smokers find that lung acetaldehyde levels far higher for smokers than non-smokers. Jauhanen, et. al., “Origin of Breath Acetaldehyde During Ethanol Oxidation:  Effect of Long-Term Cigarette Smoking,” 100 J. Laboratory Clinical Med. 908 (1982).

Acetaldehyde levels in alcoholics are 5 to 55 times higher than normal.  Lindros, et. al., “Elevated Blood Acetaldehyde in Alcoholics and Accelerated Ethanol Elimination,” 13 (Supp. 1) Pharmacology, Biochemistry & Behavior 119 (1980).  Breath acetaldehyde levels show  blood-alcohol levels 30 times higher than would be expected from direct blood analysis.” Stowell, et. al., “A Reinvestigation of the Usefulness of Breath Analysis in the Determination of Blood Acetaldehyde Concentration,” 8(5) Alcoholism:  Clinical & Experimental Res. 442 (1984); Taylor and Oberman, Drunk Driving Defense, § 7.02 at pp.  at 541 (citation omitted). Diabetes is also a major source of acetaldehyde.  Id.

In sum, chemicals produced naturally in the body, such as acetaldehyde, and even ingested through environmental exposure (such as toluene), interfere with breath testing device accuracy.  Worse, when present, interfering substances add to a defendant’s computed blood alcohol level.  Put in the perspective of the National Research Council’s report, the non-specific nature of breath testing makes it a poor scientific methodology because it is capable of inaccuracy when interfering substances create machine inaccuracy.