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Breathalyzer Inaccuracies in Maryland DUI Cases

Probably the most significant misconception is on their accuracy. We believe that most people just believe that breathalyzers are completely accurate and they provide an accurate extrapolation of an individual’s blood alcohol content. Based on our experience practicing in this area of law, we do not believe that to be the case.

Probably the most significant of those general problems is going to be using the same Partition Ratio for all individuals who submit to breathalyzer tests. Let’s talk a little bit about what the Partition Ratios are and why they can be different.

Partition Ratios

Breathalyzer tests extrapolate the amount of alcohol in an individual’s blood from a sample of one’s breath. What that means is that the breathalyzer tests will measure the amount of alcohol exhaled by an individual and then multiply that by a number, essentially an arbitrary number, to convert that breath alcohol into blood alcohol.

Now the breath alcohol breathalyzer testers will use the same exact Partition Ratio for everyone who blows into the breathalyzer. They are going to say the exhaled ratio of breath alcohol and blood alcohol is going to be same for the 120-pound endurance athlete versus a 500-pound man, and it will be the same for a 20-year-old male and an 80-year-old female. That is obviously not correct.

Different individuals will have different ratios of breath alcohol to blood alcohol that are not captured by the Partition Ratio that the breathalyzer machines use. That is another factor that renders breathalyzer testing inherently inaccurate for individuals whose true Partition Ratio varies very significantly from the Partition Ratio used by the breathalyzer machines.

False Positives and Inaccurate BAC Results

First, one that we have already discussed is based upon the Partition Ratio. The Partition Ratio can differ for people who have a low body weight and females because they actually tend to have lower partition ratios than heavy male individuals.

There are some other ways that breathalyzers can provide inaccurately high readings as well. One of those is by mouth alcohol. Now officers are supposed to observe an individual for 20 minutes prior to allowing that person to blow into the breathalyzer and that observation needs to be close and continuous, meaning that they have to be really looking at the individual and they cannot look away and they cannot do that observation period with their backs turned towards the individual.

The purpose of the observation is to make sure that the individual does not regurgitate during the 20 minutes prior to the test. If that happens that can cause particles of food or other matters to be held in the mouth or teeth and when an individual blows through that that will cause the reading in the machine to be higher than it otherwise would have been because it is not measuring blood alcohol rather it is measuring mouth alcohol. I have seen many situations where officers are extremely lackadaisical in their approach to the 20-minute observation period, which causes significant issues of higher readings.

Government Experts

Government experts are absolutely aware of the issues regarding breathalyzer testing. They know the Partition Ratio and that applying same Partition Ratio across all individuals has no scientific validity. As to why they use them, as with many of the answers from the government, it is because that is the cheapest alternative. A program of blood testing would be extremely expensive to administer and I think would run into a lot of pushback from the legislature if attempted to be implemented. I think that the government does the breath testing because it is cheaper and easier than some of the other alternatives.

Maryland Breathalyzers in DUI Cases
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