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Minnesota Source Code Debacle Leads to End of Breath Testing

by ptbarone on May 31, 2009 has discussed source code in several prior posts.  These posts include a discussion of the current status of this litigation in Minnesota involving the Intoxilyzer 5000 breath machine.  Now, because of an April state Supreme Court decision, prosecution of cases involving breath tests have been halted until defendants have obtained the Intoxilyzer source code, allowing them to determine if it has been calibrated correctly and the results are reliable.

According to DL-Online, “[T]he larger ramifications are that prosecutors throughout the state could be stymied by the ruling and be forced to dismiss hundreds, perhaps thousands of pending DWI cases.”

Because of this problem, Minnesota police in at least one county who arrest individuals under suspicion of drunk driving will no longer be offering breath tests.  Such drivers will be offered only blood or urine tests.

The report indicates that “[S]uspected drunken drivers in Hubbard County will either have to urinate into a cup or give a blood sample after being pulled over if they flunk a field sobriety test.”

Breath tests have become the preferred method of determining a suspected drunk driver’s bodily alcohol content because breath tests are easy to administer and relatively non-invasive.  There are however many potential problems with breath testing.  Here is a very brief list from

Possible Defenses to the Breath or Blood Test

Evaluation of DUI/DWI Cases

  1. Only the direct analysis of blood alcohol (e.g. by gas chromatography or enzymatically) accurately determines the blood alcohol concentration (BAC) of every driver for a given time. This assumes proper sample collection and storage procedures are employed. Breath, urine and saliva alcohol levels have not been shown to correlate well with the BAC for given sample times. If possible, a direct BAC should be determined as close in time to the DUI stop as possible. Multiple determinations of BAC, over time, may be desirable, as discussed below, but are virtually never performed.
  2. No breath analyzer, regardless of manufacturer or particular features, has ever been independently demonstrated to be accurate in predicting the blood alcohol of every driver of a large group. “Outliers” are common in all of the published studies. Based on breath analysis, the BAC estimated may easily be two-fold or greater than the actual BAC determined in these outliers, at approximately the same time. The bottom line is breath alcohol analysis should only be used as a screen, as a matter of convenience. If intoxication is suspected based on breath analysis, it must be immediately confirmed with a direct BAC determination. The presumption that breath analysis is definitive for everyone in the estimation of their BAC is completely unsupportable scientifically.
  3. Many “biological” factors have been shown to affect the estimation of the BAC by breath analysis, most of which are independent of the breath analyzer used. These include alcohol contamination of the breath sample (the blow) to be analyzed with non-breath alcohol sources, individual differences in alcohol transfer from blood to breath, and other procedures that introduce error in the breath alcohol collection and subsequent alcohol analysis by a breath analyzer. Also evaluation of the food and beverage consumption by the individual prior to the DUI/DWI stop, his or her performance on field sobriety tests (FSTs) and arresting officer’s observations, relevant medical and/or prescription records, and general demeanor on video can aid assessing whether the breath alcohol analysis result was likely correct in establishing that he or she was intoxicated at the DUI/DWI stop.
  4. It is usually not possible to accurately estimate the BAC for a previous time period, i.e. when the DUI/DWI occurred, based only on one BAC determination, regardless of how it was estimated. One possible exception is when the breath analysis occurs within minutes of the DUI/DWI stop.
  5. The rationale for these statements is that it is imperative to know whether the BAC was constant, increasing, or decreasing at the time that it was determined. An increasing BAC generally indicates that alcohol is being absorbed (i.e. during the absorption phase), while a decreasing BAC indicates that primarily metabolism and excretion of alcohol are occurring (i.e. during the post-absorption or elimination phase). A constant BAC over a time period indicates that the rate of alcohol absorption is approximately equivalent to the rate of its metabolism and excretion. In the case where only metabolism and excretion are occurring, i.e. during the elimination phase, it may be possible to predict what the BAC was previously for short periods of time since alcohol is metabolized at a constant rate by the liver and excreted via the urine. However, this elimination rate, itself, varies somewhat from person to person. Using an average metabolic or elimination rate to extrapolate back in time may provide an estimate of the BAC only. It does not determine the precise BAC for that individual and sample time. Unfortunately, in most DUI cases, data is not sufficiently adequate even to determine when and how long only the elimination phase occurred. Thus, a back extrapolation is usually highly unreliable in estimating the BAC for that time.
  6. Many factors have been reported that affect the rate of alcohol absorption and the appearance of BAC. For example, these include factors influencing the rate of stomach emptying. Once the stomach is emptied of the alcohol it contains, that alcohol is rapidly absorbed by the small intestine and appears in the blood. If the stomach does not empty for hours, there can be a substantial delay in the appearance of significant BACs after drinking intoxicating amounts. Relatively little alcohol is directly absorbed by the stomach, itself. Evaluating the importance of these factors in a particular DUI/DWI case may aid in determining the likelihood that blood alcohol was increasing or decreasing at the time of the DUI/DWI stop.

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