DWI and DUI Facts and Fiction: Urban Myths, Urban Facts

Many myths surround the subject of DWI and DUI. (Other initials are sometimes used in states.) Scientific facts are used to correct some of those myths. It’s fun to discover DWI and DUI facts and fiction. Share them with your family and friends!


DWI and DUI Facts and Fiction

Myth:DUI facts

Sucking on pennies will lower a person’s blood alcohol concentration (BAC) reading.


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!


“Alcohol on the breath” is a reliable sign of alcohol drinking and intoxication.


Alcohol is actually virtually odorless. The odor of things commonly found in alcoholic beverages is what people perceive as alcohol. The breath odor from drinking a non-alcoholic beer is the same as that from drinking an alcoholic one.

Research using experienced police officers shows that odor strength estimates are unrelated to actual BAC. In the study it ranged from zero to .13. That’s almost twice the legal limit for driving. The estimates made by the officers were no more accurate than random guesses. The researchers found that estimates of alcohol on the breath are unreliable.2

DUI facts Myth:

People who abstain from alcohol are “alcohol-free.” Therefore, they can’t be arrested for DUI.


The human body produces its own supply of alcohol naturally on a continuous basis, 24/7. It’s “endogenous ethanol production.” So we always have alcohol in our bodies. And in some cases people produce enough to become legally intoxicated and arrested for DUI.3


Diabetics suffering hypoglycemia have symptoms that can cause them to fail field sobriety tests. Symptoms include disorientation, staggering, drowsiness and poor motor control. But a breathalyzer will clear them from suspicion of DWI or DUI.


Hypoglycemia causes acetone in the breath. A breath tester may record as acetone as alcohol. And about one of seven drivers is diabetic. So they’re at risk of false arrest and conviction for DUI or DWI.4 See False Breath Tester Results from Acetone in Breath.


Field sobriety tests accurately identify intoxicated drivers.


DUI factsResearchers showed police officers videotapes of individuals taking six common field sobriety tests. The officers then identified which suspects were too intoxicated to drive legally. Unknown to the officers, none of the suspects had a BAC above 0.000. They had zero alcohol in their blood. However, the professional opinion of the officers was that 46% of the completely sober individuals were illegally intoxicated! Therefore, field sobriety tests led to judgments by police that were about as accurate as flipping a coin.5

That’s why lawyers say you should never, ever take a field sobriety test.


Breathalyzers and other breath testers are accurate.


DUI facts and fictionThere are many, many sources of error in breath machines. For an explanation of some of them visit Accuracy of Breath Testers.

Smoke? Here’s something to think about. Breath testers can falsely record acetaldehyde in the breath as alcohol.

Acetaldehyde levels in the lungs of smokers are much higher than 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 or 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.

      Lack of precision
Prof. Lawrence Taylor
Prof. Lawrence Taylor

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 and Haynes v. State. In addition, State v. Boehmer recognizes an even larger .0165% inherent error).6

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

Would this be 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?


A person accused of DUI or DWI can demand a jury trial to contest the results of a BAC machine.


DUI factsThe right to a jury trial is fundamental to English law since the Magna Carta. The framers of the U.S. Constitution considered it essential.  That’s why 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.

You may have overwhelming evidence that proves your BAC reading is erroneous. Yet many states will deny you a jury trial.7 See DUI and the Disappearing Right to a Jury Trial.


Police officers can’t influence the BAC reading of a breath testing device.


DUI factsOfficers can and do influence BAC readings. Lawrence Taylor quotes Dr. Michael Hlastala. He’s 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


Alcohol breath testers measure BAC.


DUI FACTSAlcohol breath testers don’t actually measure BAC. It takes analyzing a sample of blood to do that. Breath testers try to measure alcohol in the breath in order to estimate the BAC. That’s why not all states permit their use.

There’s a 20-30 percent inherent margin of error in alcohol machines under ideal conditions. So it’s 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 a third is to select a designated driver. For specific tips on these practical solutions visit Breath Analyzer.

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

      False Assumption

Breath testers also assume as constants certain ratios within the human body. But these 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 conversion ratio. That is, in converting alcohol in the breath to estimates of alcohol in the blood.

But this ratio varies from 1,900 to 2,400 among people. And, of course, also within a person over time. This variation will lead to false BAC readings. Some breath test 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.10 For more visit Alcohol Breath Analyzer Accuracy .

Alcohol breath machines are really only BAC estimators.


You now know some DWI and DUI Facts and Fiction. Enjoy them with your family and friends!

Readings for DUI Facts

Footnotes for DWI and DUI Facts and Fiction

1. www.snopes2.com/. There is no scientific evidence that sucking on copper has any effect on alcohol breath tester BAC results. And no scientific report suggests that it does.

2. Moscowitz, H., et al. Police officers’ detection of breath odors from alcohol ingestion. Acci Analysis Prev, 31(3), 175 180.

3. Lindiger, W., et al. Endogenous production of methanol after the consumption of fruit. Alco Clin Exper Res, 21, 939-943.

4. Brick, T. Diabetes, breath acetone and Breathalyzer accuracy. Alco Drugs Driv, 9(1).

5. Cole, S. & Nowaczyk, R. Field sobriety tests. Are they designed for failure? J Percep Motor Skills, 79, 99-103.

6. Taylor, L. Close Enough for Government Work.

7. Taylor, L. DUI and the Disappearing Right to a Jury Trial.

8. Hlastula, M. Physiological errors associated with alcohol breath tests. Champion, 9(6).

9. Taylor, L. How to Fool the Breathalyzer.

10. Jauhonen, P., et al. Origin of breath acetaldehyde during ethanol oxidation. J Lab Clin Med, 100(6), 908-916.


    • This site gives no advice. Please see a lawyer for DUI facts or questions.