DWI/DUI Facts & Fiction: Urban Myths

by David J. Hanson, Ph.D.

The subject of DWI and DUI is surrounded by common myths which are corrected here with scientific information and evidence.

Myth: Sucking on pennies will lower a person’s BAC reading.

Fact: Sucking on pennies or other copper has no effect on alcohol breath tester BAC results. 1 Don’t be a sucker... it makes no cents!

Myth: “Alcohol on the breath” is a reliable sign of alcohol consumption and intoxication.

Fact: Alcohol is actually odorless.... it has no smell. What people perceive as alcohol on the breath is actually the odor of things commonly found in alcoholic beverages. The breath of a person who drinks a non-alcoholic beer will smell the same as that of a person who has consumed an alcoholic beer.

Research using experienced law enforcement officers has found that odor strength estimates are unrelated to blood alcohol concentration (BAC), which ranged in the experiment from zero to .13 (almost twice the legal limit for driving). The estimates made by the officers were no more accurate than random guesses. The researchers concluded that estimates of alcohol on the breath are unreliable. 2

Myth: People who abstain from alcohol are "alcohol-free" and can’t be arrested for DUI.

Standard Drinks

Standard Drinks graphically illustrates information on the equivalence of standard drinks of beer, wine and distilled spirits or liquor. Its accuracy has been established by medical and other health professionals.

Fact: The human body produces its own supply of alcohol naturally on a continuous basis, 24 hours a day, seven days a week. It’s called endogenous ethanol production. Therefore, we always have alcohol in our bodies and in some cases people produce enough to become legally intoxicated and arrested for DUI. 3

Myth: A Breathalyzer will clear from suspicion those diabetics suffering hypoglycemia, whose slurred speech, disorientation, staggering, drowsiness, poor motor control, and flushed face cause them to fail field sobriety tests.

Fact: Hypoglycemia causes acetone in the breath, which the Breathalyzer will record as alcohol on the breath. Unfortunately, about one of seven drivers is diabetic and at risk of false arrest and conviction for DUI/DWI. 4

Myth: Field sobriety tests, being based on scientific principles, accurately identify intoxicated drivers.

Fact: A study conducted by scientists at Clemson University involved showing police officers videotapes of individuals taking six common field sobriety tests. The officers were asked to decide whether suspects were too intoxicated to drive legally. Unknown to the officers, none of the suspects had a BAC above .000. They had zero alcohol in their blood. However, in the professional opinion of the officers, 46% of the completely sober individuals were too drunk to drive! Therefore, use of field sobriety tests led to judgments by law enforcement officers that were about as accurate as flipping a coin. 5

Myth: Breathalyzers and other breath testers are accurate.

Fact: There are many, many sources of error in breath testers. For an explanation of some of them visit Breath Analyzer Accuracy.

Smoke?

Here’s something to think about. Acetaldehyde is a compound in the breath that is falsely recorded as alcohol by breath analyzers.

Important for tobacco smokers is the fact that acetaldehyde levels in their lungs are much, much higher than those in the lungs of non-smokers. 10 This means than smokers are far more likely to have falsely high readings on a Breathalyzer or other machine.

The danger of arrest and false conviction of DWI/DUI is yet another reason to quit smoking.

Even in the absence of any of these common problems and under ideal conditions, alcohol breath testers simply lack precision. Law professor and attorney Lawrence Taylor explains that “Scientists universally recognize an inherent error in breath analysis, generally of plus or minus .01%.” In addition “This has been acknowledged by courts across the country (see, for example, People v. Campos, 138 Cal. Rptr. 366 (California); Haynes v. Department of Public Safety, 865 P.2d 753 (Alaska); State v. Boehmer, 613 P.2d 916 (Hawaii), recognizing an even larger .0165% inherent error). 6

This means that under ideal conditions, which is a highly unlikely situation, a BAC reading of .08 reflects an actual BAC of anywhere from .07 to .09 or even .065 to .095. That’s a margin of error of 20 to 30 percent.

Would this be considered a reasonable margin of error for an accountant, airline pilot, or bank teller? Is this a reasonable margin of error in court, where guilt should be proved beyond a reasonable doubt?

Myth: A person accused of DWI or DWI can demand a jury trial to contest the results of a BAC estimator machine, with its “ideal conditions” 20-30 percent margin of error, especially if there are good reasons to question the accuracy of the results.

Fact: The right to a jury trial is fundamental to English law since the Magna Carta and the framers of the United States Constitution considered is so essential that they included it in the Bill of Rights. The Sixth Amendment states

"In all criminal prosecutions, the accused shall enjoy the right to a speedy and public trial, by an impartial jury of the State and district wherein the crime shall have been committed..."

The Sixth Amendment provides no exceptions to this fundamental right to a trial by jury in all criminal cases.

Although you may have overwhelming evidence of many types and from many sources that prove your BAC reading is erroneous and that you are innocent of DWI, many states will deny you a jury trial. 7

Myth: Law enforcement officers can’t influence the BAC reading of a breath-testing machine.

Fact: Law enforcement officers can and do influence BAC readings. Law professor and lawyer Lawrence Taylor quotes Dr. Michael Hlastala, Professor of Physiology, Biophysics and Medicine at the University of Washington

"By far, the most overlooked error in breath testing for alcohol is the pattern of breathing.... The concentration of alcohol changes considerably during the breath...The first part of the breath, after discarding the dead space, has an alcohol concentration much lower than the equivalent BAC. Whereas, the last part of the breath has an alcohol concentration that is much higher than the equivalent BAC. The last part of the breath can be over 50% above the alcohol level....Thus, a breath tester reading of 0.14% taken from the last part of the breath may indicate that the blood level is only 0.09%." 8

Professor Taylor explains that

“Many police officers know this. They also know that if the machine contradicts their judgment that the person they arrested is intoxicated, they won’t look good. So when they tell the arrestee to blow into the machine’s mouthpiece, they’ll yell at him, "Keep breathing! Breathe harder! Harder!" As Professor Hlastala has found, this ensures that the breath captured by the machine will be from the bottom of the lungs, near the alveolar sacs, which will be richest in alcohol. With the higher alcohol concentration, the machine will give a higher -- but inaccurate - - reading.” 9

Myth: Alcohol breath testers measure the concentration of alcohol in a person’s blood stream (blood alcohol concentration or BAC).

Fact: Alcohol breath testers don’t actually measure BAC, which can only be done by analyzing a sample of blood. They attempt to measure alcohol in the breath in order to estimate the concentration of alcohol in the blood. That’s why not all states permit their use.

Given the 20-30 percent inherent margin of error in alcohol machines under ideal conditions, it would be wise to avoid being subjected to such an invalid device.

There are good ways to virtually eliminate being unfairly convicted of impaired or intoxicated driving by a BAC estimator. One is to choose not to drink, another is to pace the rate of drinking and follow other tips for maintaining a low BAC, and another is to select a designated driver. For specific tips on these practical solutions visit Breath Analyzer

In reality, alcohol breath testers detect any chemical compounds that contain the methyl group in its molecular structure. Unfortunately, there are thousands of such compounds. Many occur naturally in the human breath or are picked up from disease; inhaling fumes from gasoline, glue, paint, paint remover, “new car smell,” celluloid, cleaning fluids, etc.

Breath testers also assume as constants certain ratios within the human body that actually vary widely from person to person and within the same person over time. For example, many breath-testing machines assume a 2,100-to-1 ratio in converting alcohol in the breath to estimates of alcohol in the blood. However, this ratio varies from 1,900 to 2,400 among people and also within a person over time. This variation will lead to false BAC readings. Some breath analysis machines assume a hematocrit (cell volume of blood) of 47%. However, hematocrit values range from 42 to 52% in men and from 37 to 47% in women. A person with a lower hematocrit will have a falsely high BAC reading. These machines appear to discriminate against female suspects. For more visit Breath Analyzer Accuracy.

Alcohol breath machines are really BAC estimators.

This site does not provide legal opinion or advice and none should be inferred. For legal information always consult a qualified attorney.

References and Readings

filed under: Drinking and Driving

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