What is the debate over the Intoxilyzer's reliability and accuracy?

Proponents of the Intoxilyzer say it will only show a result from absorbed breath (deep lung air) alcohol and nothing else. However, opponents say that the Intoxilyzer often misreads other commonly found substances in human breath and erroneously gives high readings saying that they are from alcohol.

Of particular importance here are the following facts. First, the DWI alcohol concentration law says a person is intoxicated when he has a .08 concentration in his breath, but, it does not say .08 by Intoxilyzer. This fact means that no judge or jury is required to believe that an Intoxilyzer result of .08 or more is accurate or reliable.

Second, neither the manufacturer nor the DPS will allow anyone, other than law enforcement personnel, to test either the machine's accuracy or its reliability. It is generally understood that for a procedure to be accepted as accurate and reliable in science, that it must be open and available for the scientific community to test and retest the procedure. This is not the case with the Intoxilyzer.

Third, the manufacturer says it does not warrant that the Intoxilyzer is fit for any particular purpose. This fact clearly is an implicit admission by the manufacturer that its machine is not even warranted as accurate and reliable for breath testing.

Fourth, the Intoxilyzer is capable of breath preservation, however, our DPS purposely fails to require the breath specimens to be saved. The cost of preservation would be less than $2.00 per test and would allow an opportunity for the person charged with DWI to check the accuracy of the sample. And, if found to be inaccurate, attack the validity of the prosecutor's test. Indeed, it is a generally accepted scientific fact that the re-testing of preserved breath specimens, which is done by a method known as gas chromatography, is a more accurate and reliable means of breath alcohol concentration testing than that done by the Intoxilyzer.

Fifth and last, the Intoxilyzer's working design is premised on the assumption that every person tested is exactly the average person. All persons are not exactly average! Human beings come in all different sizes, weights, ages, muscle tones, lung capacities, alcohol tolerances, temperatures, hematocrit levels (amount of solids in the blood) and blood/breath ratios (the number of times an item appears in the blood vs. the number of times the same item appears in the breath). Automatic and undetected error can be illustrated by simply having the person tested not be exactly average. In this regard, it should be noted that the Intoxilyzer assumes a blood/breath ration of 2100/1 (i.e., 2100 parts of alcohol in the blood for every 1 part of alcohol in the breath) for every person tested. Here, it can be noted that a majority of persons have a blood/breath ration of 2100/1 or greater. Persons with a higher blood/breath ration of 2100/1 will not be prejudiced by the Intoxilyzer's assumption. However, persons with a lower blood/breath ration will be prejudiced because the Intoxilyzer will erroneously read too high of an alcohol concentration result, thus potentially causing a person who should test at .04, .05, .06, etc. to actually test out at .08, .11, .12, etc. Of particular import here is the fact that scientists have documented persons with blood/breath ratios as low as 1100/1.

This same type of prejudice also occurs where the person tested is not exactly average with respect to other bodily functions: muscle development, temperature, hematocrit level, etc. Moreover, since the machine was built by humans, is serviced by humans, and is operated by humans, it is subject to human error just like all other machines. The above facts conclusively demonstrate that the Intoxilyzer, even if it is properly working and is being properly operated, because the person being tested is not exactly average, can label an innocent person as guilty.