The general idea behind breath testing is that the breath-test measures the amount of alcohol in a deep-lung breath sample. That amount is then translated to BAC using a chemical analysis using such scientific methods as infrared spectrophotometry, gas chromatography or fuel-cell detection.
With an infrared system, the most commonly used and most advanced of the three above examples, breath is blown into a chamber. Then an infrared beam is shot through the chamber and alcohol molecules are absorbed by the beam. The beam is reduced in size as it passes through the chamber and is then measured. The more light absorbed, the higher the reading on the machine. Computer software then translates the results to BAC for the average human.
The resulting ratio computed by the software describes the relationship between breath alcohol content and blood alcohol content. The number that is computed defines the breath quantity that contains the same amount of alcohol as a given blood quantity. The value of 2100:1 is legislatively accepted as the population average and has been almost universally adopted. Translated, this means 2100 parts of breath contain the same quantity of alcohol as 1 part of blood.
The test results that are computed by the breath test machine may also be affected by other issues involving the test subject. These personal issues may include age; lung function, overall strength and size, a disease or condition such as asthma, diabetes, eardrum rupture, ketosis, emphysema, bronchitis, dental issues, fever or harelip, shock or trauma, certain types of special diets, or hiccoughing, burping, vomiting or hyperventilating. Heartburn can make breath results unreliable particularly if the individual suffers from a severe form of acid reflux called GERD (Gastroesophageal reflux disease).
In addition to human (subject) factors that may affect the accuracy of the breath test machine there may also be technical issues that could affect the accuracy of the results. Such technical issues could include (depending on the machine used):
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*photo of a NHTSA billboard, Everett, Washington
• Temperature low
• Temperature high
• Printer error
• CRC error
• Pump error
• System won’t zeroThe breath test machines can be temperamental and on occasion prone to error. While it is not necessary to understand every working component of these machines, it is imperative that your attorney examine the records (available online) of your particular machine to ensure that your machine didn’t encounter any malfunctions prior to or after your breath sample was provided.
Breath testing in the DUI context has remained the work horse over the years in providing law enforcement with scientific evidence of impairtment. Law enforcement has advocated that breath testing remains a relatively reliable form of obtaining the BAC from an individual and furthermore, it remains a relatively inexpensive manner of evidenciary testing. Naturally there is also much criticism regarding the relIability of breath testing.
There is little debate in the DUI community that breath testing is an inferior method of testing an invidivual’s blood alcohol concentration in comparison to blood. However, it is equally agreed that breath testing does have some advantages over a blood draw, those primarily being that it is cheaper, faster, gives immediate results, and is less invasive.
The biggest problem with a breath test compared with a blood test is reliability. Since the 1970s, researchers have warned scientists and those who use breath testing devices of factors that can affect a reliable breath alcohol (BAC) reading. Mason, M., Dubowski, K.,Breath-Alcohol Analysis: Uses, Methods, and Some Forensic Problems. Review and Opinion. J Forensic Sci. (January, 1976) The primary factors that can potentially affect the accuracy of a breath testing machine include physiological factors, machine characteristics, and administrative practices.
In the State of Washington the BAC Datamaster, the BAC Datamaster CDM and the Draeger BAC machine are the only machines certified for use in DUI cases.
The breath test’s service guides also list the following possible error messages on the machine’s LCD display, which may include:
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• The machine must be warmed to the correct operating temperature;
• The simulator solution must be kept at 34 degrees centigrade, plus or minus 0.02 degrees; a decrease of one degree will cause a 6.8 percent decrease in the amount of alcohol, resulting in a falsely higher BAC reading for tested breath samples. A thermometer attached to the simulator is supposed to be checked by the operator;
• The sample chamber must be heated to exactly 50 degrees. No variation in temperature is acceptable. This is monitored by the machine’s computer;
• The detector must be cooled to a temperature almost to freezing. This is also monitored by the machine’s computer;
• The breath tube must be heated to 50 degrees and if not properly heated condensation can form in the tube which can capture alcohol during a test and be picked up by later breath samples. Despite the need for a 50 degree temperature, the Operator’s Manual tells the operator only to “check that the mouth piece is warm or hot to the touch;”
• An adequately deep lung sample must be ensured;
• The equipment must be maintained properly, calibrated correctly and cleaned adequately;
• Other items such as mouthwash or adhesive, or lip ointment can affect test results (a proper mouth check would likely eliminate this potential problem);
• Police radios may cause radio frequency interference (RFI) with the testing equipment;
• The subject may have had exposure to a gas or vapor such as paint, floor sanding, varnishing or other chemicals;
• Outside environmental causes in the surrounding air may cause inaccurate test results.
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