Breathing into a Intoxilyzer can feel like testifying against oneself. From the perspective of the person being subject to a breath test, there is no reasoning with it, and no arguing against it. Our faith in modern technology means that technology cannot lie. Or so police officers, prosecutors and their expert witnesses would like you to believe.
But is that really the case? Are breathalyzer/Intoxilyzer tests infallible?
Part of establishing the existence of a reasonable doubt when it comes to defending against charges of drunk driving can require challenging the technology that police and prosecutors use as evidence to back up those charges. Understanding the details of how breathalyzer tests work is the foundation for being able to look for ways that they may have given an inaccurate result.
There are multiple factors that can influence the accuracy of a breathalyzer’s readings. This post will cover a few examples.
Does the concentration of alveolar air in a breath sample make a difference? At least one study suggests that alcohol exchanges from the bloodstream to the lungs in the upper airway. This may affect the result of a test depending on the lung volume of the person providing a breathalyzer sample, because people with larger volume may provide a sample with less alveolar air, which in turn may produce a lower concentration of alcohol.
Do breathing patterns have an influence on breathalyzer results? It may be that some breathing behaviors may increase alcohol concentration in the test sample. These include holding one’s breath, or keeping one’s mouth closed for five minutes beforehand, both of which may increase the concentration. Even heartburn (gastric reflux) or belching may have an effect; the presence of residual alcohol, or even small amounts of stomach contents or gas can create an artificially high reading. The author has performed his own tests on his Intoxilyzer 8000 (the machine used in Oklahoma) and was able to vary the score .03 either direction just by instruction the test subject different ways to blow in the machine. (There are only two Intoxilyzer 8000s in private hands in Oklahoma and the author co-owns both machines.)
Can substances other than alcohol affect the test result? Evidence suggests that exposure to some chemicals, such as paint thinner or lacquer, can trigger a breathalyzer test reading in the same way that alcohol does. Even the fuel cell used in some devices can end up reading substances other than ethanol alcohol, but may not be able to distinguish these from ethanol.
Can quality control problems affect the quality of the test sample? Instances have already occurred which demonstrate that the lack of quality assurance and quality control procedures and even outright falsification in the police laboratory environment can lead to compromise of test results. Quality control measures must begin with the preparation of the test subject and continue through recordkeeping and personnel training; breakdowns anywhere in this chain can compromise the value of the test sample as trial evidence.
Much of the potential problems with breathalyzer test results are highly technical in nature and do not lend themselves to easy analysis or application. The examples above are but a few of the ways in which breathalyzer tests, instead of being technologically infallible, can in fact lead to questionable if not erroneous results. It is among the roles of a DUI defense attorney to diligently explore all relevant possibilities through which reasonable doubt may arise at trial.