Category Archives: Duiblog

Breath Testing After “One for the Road”

It’s a common situation. You’re at a restaurant, it’s been a fine meal, you’ve paid the bill and it’s time to head home. You finish off the glass of wine and head for the car.

Bad move.

A few blocks from the restaurant, you’re stopped for speeding. The officer smells the wine still on your breath and asks you to step out of the car. A few minutes later and you’re on the way to the police station — and a breathalyzer. But you know that you and your wife each had only two glasses of wine from the bottle with dinner. The charts say that at your weight your blood-alcohol level should be around .05%, so you’re well under the .08% legal limit, right?

Wrong: the reading is .10%, your license is confiscated and you are booked for DUI.

What happened?

What happened was what the toxicologists call "absorptive stage analysis". In English, your breath sample was tested while your body was still absorbing the alcohol from the last drink. Any testing during this stage of absorption will result in falsely high blood-alcohol readings.

Explanation…..Your body will continue absorbing alcohol for roughly an hour after drinking, reaching peak blood-alcohol levels sometime before that point; the presence of food in the stomach can delay this for as much as 4 hours.During this one-hour period, the alcohol is passing from the stomach and intestine into the blood, but has not yet reached a stage of "equilibrium" — that is, uniform distribution of alcohol throughout the body.

In other words, some parts of the body will have higher levels of alcohol than others — in some cases, far higher.Since the alcohol is initially passing into the arteries, arterial blood will be much higher in alcohol content than will venous blood.

Where does the alcohol come from that is being measured by the breathalyzer?

That’s right: the arteries.

Arterial blood bathes the alveolar sacs of the lungs, and alcohol diffuses into the lung air — to be breathed out into the breathalyzer mouthpiece. As one of the most noted experts in the field of forensic toxicology has observed: "Breath is not a reliable means of estimating a subject’s BAC (blood alcohol concentration)…

There is a significant likelihood that a given subject will be in the absorptive state when tasted under field conditions. Because of large differences in arterial BAC and venous BAC during absorption, breath tests consistently overestimate the result that would be obtained from a blood test — by as much as 100% or more." Simpson, "Accuracy and Precision of Breath Alcohol Measurements for Subjects in the Absorptive State", 33(6) Clinical Chemistry" 753.

In other words, if you take a breath test within an hour or so after your last drink, you will have a false high reading — possibly twice as high as your true blood-alcohol level.

Driving a New Car? Don’t take a Breath Test!

Remember that "new car smell"? The great scent inside of that new car you bought a couple of years ago? It could get you charged with DUI…. Consider an excerpt from the Reuters news agency (Sydney, December 9, 2001):

"Australian scientists have warned that the reassuring smell of a new car actually contains high levels of toxic air emissions which can make drivers ill. A study by Australia’s main scientific body, the Commonwealth Scientific and Industrial Research Organization (CSIRO), found high levels of toxic emissions in cars for up to six months and longer after they leave the showroom… The toxic emissions include benzene, a cancer-causing toxin; acetone, a mucosal irritant; ethylbenzene, a systemic toxic agent; and xylene isomers, a foetal development toxic agent…."

So what has this got to do with breath tests? Well, one of the compounds you were actually smelling was acetone. As has been discussed in earlier posts ("Why Breathlyzers Don’t Measure Alcohol"), acetone is one of many chemical compounds which Breathalyzers will mistakenly report as alcohol. See the reasearch reported in such scientific articles as "The Likelihood of Acetone Interference in Breath Alcohol Measurements", 3 Alcohol, Drugs and Driving 1, and "Excretion of Low-Molecular Weight Volatile Substances in Human Breath: Focus on Endogenous Ethanol", 9 Journal of Analytical Toxicology 246.

And no, you don’t have to drink the stuff. Simply absorbing it through your skin or inhaling it can result in measurable levels of the compound in your body for hours or even days, which will be continually expelled in the breath….. and possibly into a judge-and-jury breathalyzer.

Why Breathalyzers Don’t Measure Alcohol

That’s right: Breathalyzers don’t actually measure alcohol. What they actually detect and measure is any chemical compund that contains the methyl group in its molecular structure. There are thousands of such compounds — including quite a few which can be found on the human breath. And this machine that determines a person’s guilt or innocence will "see" all of those chemicals as alcohol — and report a falsely high "blood-alcohol" concentration (BAC).

Most breath machines used in DUI cases by law enforcement today employ a technology called "infrared spectroscopy". The DUI suspect breathes through a tube connected to the machine and a breath sample is captured in a small "sample chamber" inside the machine. Then beams of infrared energy are shot through the captured breath sample. If there are any compounds containing the methyl group, they will absorb some of this energy; the more of the chemical compound in the breath sample, the more energy is absorbed. The more energy that is absorbed, the less infrared energy that reaches sensors at the other end of the sample chamber. And the less energy that is detected by the sensors, the higher the "blood-alcohol" reading.

Problem: the machine is designed to simply assume that the chemical compound absorbing the energy is alcohol. If a person has any of these other compounds on his breath, called "interferents" by the engineers, he will get a falsely high BAC test result. And if there are two or three such compounds on his breath, the machine will read a cumulative result: it will add them up and falsely report the total as the blood-alcohol level.

So what kinds of compounds may be on a person’s breath that can cause false BAC readings in a DUI case? In one study of eight men, 69 different compounds containing the methyl group were discovered. "Trace Composition of Human Respiratory Gas", 30 Archives of Environmental Health 290. In another study invoviing 28 subjects, researchers found that teh "combined expired air comprises at least 102 various organic compounds of endogenous and exogenous origin". "Characterization of Human Expired Air", 15 Journal of Chromatographic Sciences 240. And Camnadian scientists have discovered over 200 such compounds. "The Diagnostic Potential of Breath Analysis", 21(1) Clinical Chemistry 5.

What are these compounds? Are there any on my breath?

Well, for starters, diabetics with low blood sugar can have high levels of acetone — which is "seen" as alcohol by Breathalyzers. And scientific studies have found that people on diets can have reduced blood-sugar levels, causing acetone hundreds of times higher than found in normal individuals. Frank and Flores, "The Likelihood of Acetone Interference in Breath Alcohol Measurements", 3 Alcohol, Drugs and Driving 1. And there are many other so-called "interferents". See, for example, "Excretion of Low-Molecular Weight Volatile Substances in Human Breath: Focus on Endogenous Ethanol", 9 Journal of Analytical Toxicology 246.

If you are a smoker, your Breathalyzer result is likely to be higher than expected. The compound acetaldehyde — reported by the Breathalyzer as "alcohol" — is produced in the human body as a by-product in metabolizing consumed alcohol, and eventually passes into the lungs and breath. Researchers have discovered that levels of acetaldehyde in the lungs can be 30 times higher in smokers than in non-smokers. Result: higher BAC readings on the machine.

And then there are the industrial compounds: paint, glue, gasoline, thinners, and other compounds contain the methyl group. No, you don’t have to drink the stuff: simply absorbing it through your skin or inhaling the fumes can result in significant levels of the chemical in your body for hours or even days, depending upon the "half-life" of the compound. So if you’ve painted a room or siphoned some gasoline in the last day or two, don’t breath into a Breathalyzer.

Some law enforcement officials say that this is not a problem, claiming that levels of the compound would have to be at toxic levels to raise a breath test result to .08% or higher. These officials are displaying their ignorance of the science involved — specifically, of the partition ratio. This is the ratio of the compound found in the breath to that found in the blood. With ethanol, the ratio is 2100-to-1, which means that, on average, there will be 2100 units of alcohol in the blood for every unit found in the breath.

These officials are using this ratio for all compounds, but every compound has its own ratio. Toluene (found in paint, glue, thinners, cleaning solvents. etc.), for example, has a partition ratio of only 7-to-1; a far greater amount of toluene in the blood will pass into the breath, and so a much smaller amount in the body will have a far greater impact on the breath machine.

The DUI Exception?

I have referred in many of my posts to a “DUI exception to the Constitution”, and have had numerous queries as to just what exactly this exception is.

There is, of course, no such “exception”. The term is one I have used for many years to characterize the increasing tendency in DUI cases to ignore the United States Constitution. It is easy for politically-sensitive legislators and judges to give in to the pressures of groups like Mothers Against Drunk Driving (MADD), particularly when there is no one to stand up for those whose rights are being violated. But the price is paid not only by the accused, but by all of us: it is the Constitution itself that is eroded. And the nature of our legal system is one of “precedent”: if it is permissible to ignore the Constitution in a DUI case today, then the precedent exists to ignore it in all cases tommorrow.

At some point I began using the term as the title of a lecture I’ve given to various groups of lawyers and laymen on the increasing danger to our Constitutional rights from the political pressures of well-intentioned but ignorant groups like MADD. The lectures have since been reproduced on a number of websites. For an example, see the transcript on Atlanta attorney William C. Head’s website.

Warning: Breathalyzer in Use

Have you ever noticed those "Warning: Microwave in Use" signs in restaurants? It’s for folks who have heart pacemakers: There is a risk that the electromagnetic interference (EMI) from the microwave will interfere with the electronic circuitry in the customer’s pacemaker and cause it to malfunction. This phenomenon, often called radio frequency interference (RFI), can be a recurring problem with any instrument containing electronic circuitry.

Now try to think of some place in your neighborhood that is chock full of electronic gizmos constantly transmitting RFI 24 hours a day. How about a police station? Powerful dispatch radio transmitters, radio transmitters in squad cars in the parking lot, walkie-talkies in every officer’s belt, cell phones, computer cathode ray tubes, microwave relays, electronic door locks, microwave ovens, fluorescent lighting — a veritable jungle of RFI. Now let’s put a Breathalyzer smack in the middle of this police station. An instrument filled with sensitive electronic circuitry that has to analyze tiny amounts of alcohol in breath to an accuracy of one tenth of a percent…..

Just a theory of some DUI defense attorney? Consider a report from the National Bureau of Standards, under contract with the National Highway Traffic Safety Administration to conduct accuracy testing on breath machines (referred to in the report as "Evidential Breath Testing" devices, or "EBTs"):

The Washington D.C. Metropolitan Police Department reported to NHTSA that EBTs were found to display erroneous BAC [blood-alcohol content] readings in the presence of electromagnetic fields from radio transmission…. Representatives of NHTSA and NBS were given a demonstration by police officers who routinely conduct breath testing using an EBT in a mobile van. One police officer operated his handheld radio within 1 foot of the EBT and demonstrated that the electromagnetic field could severely affect the analysis of alcohol samples.

The National Bureau of Standards subsequently conducted the testing and subsequently reported that

These results show that EMI is a potential problem with many of the EBT units currently in use….The states may have to take interim measures to determine the extent of their individual problems with EMI affecting EBTs.

The reaction by the federal government to this report was, perhaps, predictable. Afraid that it would undermine public confidence in law enforcement methods, the government classified the document and then buried it. However, it was later resurrected by a Minneapolis DUI law firm’s Freedom of Information Act lawsuit. Most manufacturers of breath machines today quietly offer an "RFI detector" as an option in their products. Unfortunately, these "detectors" are unreliable and, in any event, are rarely purchased by law enforcement agencies.

Note: all 50 states now make it a crime to drive with a blood-alcohol level of .08% or higher. In most cases, the only evidence of this comes from the breath machine. The breath cannot be re-analyzed. The machine cannot be cross-examined.