Category Archives: Field Evidence
Bryan is presently facing criminal charges for driving under the influence of alcohol. Except that he wasn’t under the influence of alcohol. He had one drink after work and was stopped at a DUI sobriety checkpoint on the way home. The officer smelled the alcohol on his breath and asked Bryan to step out of the car to take some field sobriety tests. He did fairly well on the tests but, to be sure, the officer asked him to breathe into the breath machine that had been set up at the checkpoint. The results: .09%. Bryan was arrested for DUI, handcuffed and taken to jail; his license was immediately confiscated and he was served with a notice of automatic suspension. When finally released six hours later, he was given a notice to appear in court for arraignment on drunk driving charges.
What happened? How could Bryan have only consumed one beer but registered .09% on the machine — at least four times higher than would be expected?
Well, to begin with, breath machines (commonly referred to as "Breathalyzers", although there are many competing makes and models) are notoriously inaccurate and unreliable. Calibration, maintenance, repair and use by inexperienced or poorly trained officers are always problems. And there are inherent design defects, such as being "non-specific" for alcohol — that is, they don’t actually measure alcohol; due to the nature of infrared analysis, they will report thousands of other compounds as "alcohol". Another recurring problem is "mouth alcohol".
What is "mouth alcohol" — and how could this have caused Bran’s false reading? The machine measures alcohol on the breath, and an internal computer then multiplies the reading 2100 times to get a reading of alcohol in the blood. This is because the amount of alcohol in the blood is greatly reduced as it crosses from the blood into the alveolar sacs of the lungs and into the breath; the average person has 2100 times more alcohol in his blood than in his breath (this varies widely among individuals, however, and is another inherent defect in the machines).
But what if the alcohol in the breath sample did not come from the lungs? What if the alcohol came from Bryan’s mouth or throat? Then it will not have been processed through the body, into the blood and finally out through the lungs — and it will not have been reduced 2100 times. But the machine, being a machine, will always multiply it 2100 times. Result: false high reading and Bryan is facing DUI charges.
So what was alcohol doing in Bryan’s mouth or throat?
Well, alcohol will usually stay in the tissue of the oral cavity or esophagus for about 15 minutes until it is finally diluted and flushed down into the stomach by saliva. So if Bryan had "one for the road" just before being tested, he could have a problem. Or the alcohol could have become trapped in dentures or gum cavities and lasted much longer. Bryan may have burped or belched within 15 minutes before taking the test, sending up alcohol from the beer in his stomach into his mouth and esophagus. But what actually happened was that Bryan suffers from a very common condition: GERD, or "gastroesophageal reflux disease". This causes "acid reflux", often experienced as heartburn.
Acid reflux is commonly caused by a "hiatal hernia" – damage to the pyloric valve separating the stomach from the esophagus. When the valve cannot close completely, then liquids and gasses from the stomach can rise into the throat and oral cavity, to remain there until once again flushed back down. Since a bout of acid reflux can be caused by stress, it is not unusual to find that people stopped by police officers for suspicion of DUI and subjected to field sobriety tests experience the condition.
Bryan is now ordered to breathe into the machine’s mouthpiece. With alcohol from his stomach now rising into and permeating his mouth and throat, it is mixed with the breath passing from the lungs through the throat and mouth and into the machine. Since this alcohol is being multiplied by the machine 2100 times, it takes only a tiny — invisible — amount of absorbed alcohol to cause a disproportionately high reading. In Bryan’s case, an "innocent" reading of perhaps .02% became a "guilty" .09%. And Bryan lost his driver’s license….and now has to try to prove his innocence in court.
Prove his innocence? Aren?t we presumed innocent in America? Here we have the notorious "DUI exception to the Constitution" again. Strangely, Bryan is not presumed to be innocent as we all thought: almost all state laws legally presume a person is under the influence of alcohol if if the machine’s reading is .08% or higher.
Yes, we have a system where citizens are convicted by a machine….A very fallible machine.
So what did I mean in my earlier post by "unreliable breath machines" and "passing laws against science"? Here’s just one of many examples… The computers inside Breathalyzers actually multiply the amount of alcohol in a DUI suspect’s breath sample 2100 times to get the blood alcohol concentration ("BAC"). This is because it is programmed to assume that the suspect has 2100 units of alcohol in his blood for every unit of alcohol in his breath. This is called the "partition ratio". But this ratio is only an average: actual ratios vary from as low as 900:1 to as high as 3500:1; if individual ratio is different, the BAC result will be different.
Translation: If a suspect has a true BAC of .06% ("not guilty") and a partition ratio of 1300:1, for example, the machine will give a result of .10% ("guilty"). Convicted by a machine. His crime? He was not average.
Well, when juries hear this kind of evidence, they tend to return "not guilty" verdicts. This did not sit well with MADD’s and prosecutors’ lobbyists. The result: in California and other states, drunk driving laws were changed by adding "Percent, by weight, of alcohol in a person’s blood is based upon grams of alcohol per 210 liters of breath". In other words, the law no longer cared what the actual amount of alcohol was in your blood: it was legally (not scientifically) presumed to be 2100 times what is in your breath — even though we know it is not.
The conservative California Supreme Court later found the new DUI law constitutional in People v. Bransford. But a dissenting Justice pointed out the obvious: "The majority…has on its own created the new crime of driving with alcohol in one’s breath". (Justice Joyce Kennard, 8 Cal.4th 894)
Result: today, defense attorneys are prohibited from mentioning anything about partition ratios to a jury. Scientific truth has been banned from the courtroom. And the conviction rate in drunk driving cases has risen dramatically.