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DUI expert witness opines on breathalyzer results

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Case Overview

DUI expert witness - breathalyzerThis case involves an automobile accident by a drunk driver. The plaintiff in this case was driving her two sons home from a late soccer practice. The defendant was driving herself home from a hotel bar, and she claimed that she had one glass of wine. While driving, the plaintiff stopped at a four-way intersection, with stop signs at each corner. The plaintiff saw the defendant coming, but started her vehicle, assuming that the defendant would stop at her respective stop-sign. The defendant did not slow down and struck the plaintiff’s vehicle. The plaintiff and her two sons sustained numerous injuries, with one son requiring four operations and extensive physical therapy. Immediately following the accident, the defendant submitted to a breathalyzer test, which allegedly showed that the defendant’s BAC was nearly twice the legal limit.

Question for Expert Witness

What errors are there with a breathalyzer test and how can possible errors be avoided?

Expert Witness

  • Expert Answer

“Breathalyzers are designed to estimate the amount of blood in an individual’s blood stream (BAC), providing insight into said individual’s alcoholic consumption. Errors in the readings, however, can exist, and are usually a product of incorrect measuring procedures. One specific error that can occur is by measuring the alcohol in the mouth, throat, or stomach, instead of the alcohol in the blood. Breathalyzers are designed to measure the alcoholic content in the blood, and do so by measuring the air that comes from the alveoli (which means it has been absorbed by the body and has passed from the body into the lungs). If the alcohol is being read from the mouth, throat, or stomach, however, it can give a false, increased reading. This is frequent in GERD or acid reflux patients. In order to mitigate this risk, officers should wait ten to twenty minutes after drinking has concluded to ensure that the breathalyzer can achieve an accurate result. Other factors like the machine’s calibration, the breathing patterns of the driver, and additional compounds in the blood can all interfere with the breathalyzer’s ability to provide an accurate estimation of BAC. Adequate training that reinforces the procedural steps that every officer should adhere to when administering the test can usually mitigate these risks. For example, most calibration errors can be fixed by resetting the machine, the officer should inform every driver to breath normally when breathing into a breathalyzer, and the officer should inquire about any medical conditions (which is the most frequent cause of additional compounds giving a false reading). In this case, by examining the specific steps taken by the police officer(s), I can discern the accuracy of the breathalyzer’s results, and the possible reasons for a false reading.”

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