Reader’s Question:

In a DWI case in Washington, DC, is it true that alcohol breath tester measures the concentration of alcohol in a DWI suspect’s blood stream?

Martin
Washington, DC

The breath test machines used in a DWI case in Washington, DC (or in any state for that matter) do not actually measure the blood alcohol content (BAC) of a person who is accused of DWI. The BAC could only be achieved through a blood test and the breath test machine only attempts to measure alcohol in the breath in order to estimate the concentration of alcohol in the blood. The breath test machines detect the chemical compounds that contain the methyl group in its molecular structure. There are thousands of these compounds such as celluloid, glue, cleaning fluids, paint remover, paint, acetone, asthma inhalers, gasoline, “new car smell,” etc.

The breath machine also assumes as constants certain ratios within the human body which actually vary widely from person to person and within the same person over time. An example is that the breath test machine assumes a 2,100-to-1 ratio in converting alcohol in the breath to estimates of alcohol in the blood. But this ratio varies from 1,900 to 2,400 among people and possibly within a person over time. The breath test machine also appears to discriminate against female DWI suspects. The machine assumes a body mass of an average male and don’t consider for individuals with higher body fat and it also assumes an average body temperature.

Tags: blood alcohol content, breath test, DWI, DWI lawyer