When the U.S. Supreme Court in a 5-4 decision validated DUI "sobriety checkpoints" (aka police roadblocks), Chief Justice Rehnquist admitted that they were a clear violation of the Fourth Amendment to the Constitution.   However, he wrote in Michigan v. Sitz, the "minimal intrusion" into citizens’ protected right to privacy was "outweighed" by the government’s interest in reducing DUI-caused fatalities.

Although the decision limited the use of roadblocks to apprehension of drunk drivers, it was not difficult to foresee that police would soon go beyond this.  And, in fact, there has been a growing increase in the use of roadblocks for purposes other than DUI detection.  See, for example, my earlier posts Sobriety Checkpoints: The Slippery Slope and The Slow Death of the Fourth Amendment.  Or just look around you….

Police Checkpoint Seeks Illegal Guns

Mt. Vernon, NY.  Sept. 28  -  Drivers entering the city from the Bronx via First Avenue last night encountered the first police checkpoint searching for illegal guns.

Amid flashing lights and flares in the roadway, more than a dozen officers were pulling over every third car to ask for permission to search for guns and check for other crimes such as drunken driving.

Hmmm…..Roadblocks to check for guns "and other crimes" — in other words, stopping you on the highways without probable cause to see if you’re doing anything wrong or have anything illegal in the car.  So much for the Fourth Amendment. 

But then, you don’t have to give the police your "permission to search", right?  Wrong.  Does anyone seriously believe that if you refused permission, you would be sent merrily on your way?

(Thanks to David O’Shea.)

I’ve commented repeatedly in the past about the inaccuracy and unreliability of breath-testing devices used in DUI investigations. This is due to a wide range of factors, including inherent design defects (see, for example, my previous post “Why Breathalyzers Don’t Measure Alcohol”); ineffective calibration and maintenance of the machines; improper administration of the test; radio frequncy interference; and, most importantly, physiological variability in humans.

The main problem with breath machines is that they are designed to assume all human beings are the same (see “Convicting the ‘Average’ DUI Suspect”). In fact, we are all very different from one another in ways that are critical to such testing — and we are ourselves physiologically different from one moment to the next.

Each of us, for example, is inherently different in our partition ratio — the ratio of alcohol in our breath compared to alcohol in our blood — and this ratio differs within ourselves from hour to hour (see “Breathalyzers — and Why They Don’t Work”). This is critical, as the breathalyzer will automatically compute the amount of alcohol in the blood based upon the measured alcohol on the breath — using a uniform ratio that (falsely) assumes we are all the same. Another human variable is the existence of such conditions as diabetes (see “Diabetes and the Counterfeit DUI”), acid reflux (“GERD, Acid Reflux and False Breathalyzer Results”)…. and anemia.

A person suffering from anemia has a low red blood cell count, perhaps half as much as would be normal. Put simply, when there are fewer red blood cells, the body will increase the amount of plasma to fill the void. Red and white blood cells are solid; plasma is liquid. Alcohol is attracted to liquid in the body, not muscle, bone, or other solids. It follows that the higher the ratio of liquid to solids in the blood (called the hematocrit), the higher the amount of alcohol in the blood — and the higher will be the reading on the breathalyzer.

The male-female average hematocrit is 45% (men average 47%, women 42%), but the range varies for men from 42 to 52%, and for woman from 37 to 47%. The machine, of course, assumes that all suspects have a hematocrit of 45%. The effect of an individual’s hematocrit on breath analysis can be mathematically computed. The partition ratio of alcohol in blood to alcohol in breath uniformly used in breath testing is 2100:1. If the suspect’s hematocrit is, say, 54%, the breath test result could be computed by multiplying it by 45/54. Assuming a breath test result of .09%, for example, the true blood-alcohol concentration could be determined by the formula .11 x 45/54 = .07%.

In other words, a person with a true BAC of .07% but a hematocrit of 54% would test on an otherwise “accurate” machine as .09%.  The machine "proves" the innocent citizen guilty - just because he or she is anemic (or simply varies from the statistical norm).

If you are arrested for DUI and a breath test shows a blood alcohol concentration (BAC) of .08% or higher, you are guilty. It does not matter, of course, whether you are a man or a women: the laws do not discriminate. Maybe they should…

Researchers at the University School of Medicine in Trieste, Italy, found that the stomach lining contains an enzyme called gastric alcohol dehydrogenase that breaks down alcohol, and that women have less than men. To determine the relative effects of the enzyme, they gave alcohol both orally and intravenously to groups of alcoholic and non-alcoholic men and women. They found that women reached the same levels of blood alcohol as men after drinking only half as much; with weight differences taken into account, they found that women reached BAC levels illegal in a DUI case after drinking 20 to 30 percent less alcohol than men.

The scientists’ conclusion: legislatures may need to consider sex differences in drunk driving laws when defining safe levels of drinking for driving motor vehicles. Frezza and Lieber, “High Blood Alcohol Levels in Women: The Role of Decreased Gastric Alcohol Dehydrogenase Activity and First-Pass Metabolism”, 322(2) New England Journal of Medicine 95 (1990).

Yet another study has found that women have lower “partition ratios” of blood to breath. What kind of ratios? Well, all breath machines in DUI cases measure the amount of alcohol in a person’s breath. But the what we really want to know is the amount of alcohol in the person’s blood. So how do we get that? Simple: a small computer in the Breathalyzer multiplies the amount of alcohol it detects in the breath sample by 2100 times. This is based upon the theory that, on average, there are 2100 units of alcohol in the blood for every unit of alcohol in the breath. (Note: that’s an average — but it varies from person to person.)

According to the study, women have a significantly lower partition ratio. Jones, “Determination of Liquid/Air Partition Coefficients for Dilute Solutions of Ethanol in Water, Whole Blood and Plasma”, Analytical Toxicology 193 (July/August 1983). And the lower the ratio, the higher the reading — even though the true BAC does not vary. Example: a woman with a true BAC of .06% and a ratio of 1500:1 (rather than the presumed 2100:1) will get a reading on the machine of .09% — above the legal limit. Put another way, the breath machine will show an average man accused of drunk driving to be innocent — but a woman with the same blood alcohol level to be guilty.

And then there’s the problem of birth control….

Scientists in Canada have found that “women taking oral contraceptive steroids (O.C.S.) appeared to eliminate ethanol significantly faster than women not taking O.C.S.” Papple, “The Effects of Oral Contraceptive Steroids on the Rate of Post-Absorptive Phase Decline of Blood Alcohol Concentration in the Adult Woman, 15(1) Canadian Society of Forensic Science Journal 17 (1982). That means that women will reach peak BAC faster, and return to lower levels more quickly. This, of course, can create serious problems in a DUI case when attempting to estimate BAC at the time of driving based upon a breath test administered one hour later.

Making the problem worse, researchers have also discovered that women who were taking birth control pills or who were pregnant had higher levels of acetaldehyde on their breath, due to the decreased ability to metabolize the enzyme as the level of sex steroids increases. So what? Well, most breath machines use infrared analysis in measuring the breath sample of a DUI suspect. But these machines don’t really measure alcohol, rather they measure any compound which contains the “methyl group” in its molecular structure. And acetaldehyde is one of these compounds. Result: a higher “blood alcohol” reading on the Breathalyzer. Jeavons and Zeiner, “Effects of Elevated Female Sex Steroids on Ethanol and Acetaldehyde Metabolism in Humans”, 8(4) Alcoholism: Clinical and Experimental Research 352 (1984).

It’s always a problem when the law, in its infinite wisdom, assumes that all of us are exactly the same.