In a recent post we discussed the weaknesses of Iowa's standard field sobriety tests as evidence of intoxication. Field sobriety tests are generally used as an initial indicator of intoxication; if the arresting officer concludes the tests show a driver is drunk, the next step is usually a breath test. Blood tests are considered more accurate than breath tests but they are used less often because they are considered more invasive.
Breath test machines are often generically referred to as Breathalyzers, which is actually a brand name for just one of many machines in use across the country. Iowa uses a machine called the DataMaster. This device is not infallible; in fact the DataMaster has been shown to be prone to erroneous results.
Like most breath test machines in use today, the DataMaster uses infrared light to measure the alcohol present in a driver's exhaled breath. Different levels of alcohol will result in different spectrums of light, and the DataMaster converts this spectroscopic information into a measure of blood alcohol content.
There are a number of ways to challenge breath test results in court. Some studies have shown that breath test results can differ by as much as 15 percent from blood test results, which are considered a more accurate measure of a person's actual blood alcohol content. Design flaws, improper calibration of the machine, differing results based on the machine's temperature or the driver's body temperature and different levels of hematocrit in the bloodstream are all potential grounds to attack the results of a DataMaster test.
A drunk driving arrest in Iowa is a serious matter with potentially severe consequences. An experienced OWI defense attorney who understands the limitations of breath test evidence can provide invaluable help in fighting the charges.
Source: Findlaw, "BAC Test FAQs," accessed March 20, 2016