Breath Alcohol Doesn’t Exist!

An essential fundamental of experimental science is that if something can’t be measured, it does not exist. One noteworthy scientist, Mr. William H. George, phrased it this way: “[S]cience is measurement. If I cannot make measurements, I cannot study a problem scientifically.”[i]

Understanding this primary tenant, a follow-up question might be; how precise must a measurement be in order to study something scientifically, and furthermore, if the thing being studied is not measured precisely, then does it exist at all?  These somewhat theoretical questions ought to have great significance to trial lawyers and judges, particularly in the realm of forensic science where measurements are often used to “prove” a crime.

In the context of drunk driving litigation, the relevance of these questions is obvious.  We “know” someone is guilty because his breath or blood measurement says he’s guilty.  But what do we really know about the measurement itself?  Said differently, at what point does a supposedly scientific measurement of a person’s breath become so imprecise that we can confidently say the thing measured “does not exist?”

In truth, the answer to this question might vary depending on what is being measured and who is being asked, but what never changes is the underlying principle – all measurement is uncertain, at least to some degree.  Yet, in order to know that something exists, we must be certain in our ability to measure it.

As should be expected, the science of measurement, known as “metrology,” holds that all measurements have some degree of uncertainty.  And, the only way to know how the degree or amount of uncertainty for any particular measurement has is to calculate that measurement’s “uncertainty budget.”  Properly performed, this uncertainty budget must take into consideration all potential sources of error.  A measurement that does not provide an uncertainty budget is meaningless.

Consequently, it can be said that without an uncertainty budget, the thing being measured does not exist.  In order to bring the thing measured into existence, “‘numerical data reported in a scientific paper [must] include not just a single value (point estimate) but also a range of plausible values (e.g., a confidence interval, or interval of uncertainty). This is done to ensure that the conclusions drawn from the [results] are valid.’”[ii]

The International Organization for Standardization (ISO) indicates that “it is necessary to include a measurement’s uncertainty when reporting a result because knowledge of the uncertainty associated with measurement results is essential to the interpretation of the results. Without quantitative assessments of uncertainty, it is impossible to decide … whether laws based on limits have been broken.”[iii]  Thus, without a reported range (confidence interval) it should be impossible for juries to decide if a person is guilty in a drunk driving case.

The sad truth is juries aren’t provided with this essential information, and worse than this, they don’t know they don’t know.  And so, in Michigan it is quite possible for a person to be wrongfully convicted of drunk driving.

If you have been charged with drunk driving, then it is important for you to hire a lawyer who understands science and scientific evidence.  Otherwise, it is entirely possible for you to be wrongfully convicted based on a breath or blood test result that in truth “doesn’t exist.”