The California Supreme Court has entered a ruling allowing motorists accused of driving under the influence of alcohol (DUI) to question the reliability of the breathalyzer machinery used to secure convictions. The decision, however, leaves room for the conviction of drivers even when the machine is proved unreliable. The high court recognized that a breath testing machine does not directly measure the alcohol content in a person’s bloodstream. Rather, the device estimates from a sample of breath how much alcohol might be present in the blood using a conversion factor called the “partition ratio.” California’s breathalyzer machines assume that the amount of alcohol in 2100 milliliters of breath is equal to the amount of alcohol in 1 milliliter of blood.
“Simply put, the machines all automatically convert the amount of alcohol tested in the tiny amount of breath taken from the suspect,” California DUI attorney Lawrence Taylor explained. “The internal computer multiplies the amount by 2100 — using the average ratio of alcohol in blood to alcohol in breath — to estimate the amount of alcohol in the suspect’s blood. Problem: We are not all average. And ratios vary from 1300:1 to 3500:1.”
Timmie Lance McNeal appealed his conviction for driving after his breath test showed a reading of 0.10, but the lower court refused to consider scientific evidence that at least one-third of the population has a partition ratio different from the one presumed by the breathalyzer machine. For that reason, he argued, he should not have been automatically presumed to be under the influence based solely on the machine’s readout. McNeal was convicted.
In 1989, the state legislature codified the partition ratio of 2100:1 and made it a “per se DUI” offense to have a breath test reading of .08, regardless of whether the motorist was actually intoxicated or not. This crime would be treated separately from “general DUI” which requires a motorist actually to be intoxicated.
“The legislature passed section 23152(b) to facilitate the prosecution of drunk drivers,” Justice Carol A. Corrigan explained in the unanimous ruling. “The creation of a per se DUI offense did away with the need to prove the defendant was actually impaired.”
The court admitted that the legislature’s presumption of a certain ratio could, in some cases, result in incorrect measurements.
“If, however, the defendant’s own partition ratio at the time of testing is lower than the standard ratio, conversion of the breath result using the statutory formula produces an artificially high measure of his blood alcohol,” Corrigan wrote. “2100-to-1 ratio overstates the actual amount of alcohol in his blood. For someone with an extremely low ratio of 1100 to 1, for example, use of the 2100-to-1 partition ratio would overstate blood-alcohol content by almost 50 percent.”
With this in mind, the supreme court held that partition ratio evidence may now be raised as a defense to a general DUI charge. The court, however, in previous rulings made it clear that motorists could be convicted of per se DUI regardless of any scientific evidence regarding actual intoxication. The high court cited Lawrence Taylor as an authority on the subject three times in its decision, but Taylor blasted the decision as irrational.
“It takes a supreme court ruling to allow a citizen accused of DUI to defend himself with established scientific truth,” Taylor wrote. “But in a typical retreat from logic, the court limited the admissibility of partition ratio evidence to defending against the charge of driving under the influence — not to the accompanying charge of driving with .08 percent blood-alcohol concentration (BAC). So you can use scientific facts that the BAC reading is faulty to defend yourself against the BAC-based presumption of being under the influence — but not against the charge that your BAC was .08 percent or higher.”
A copy of the decision is available in a PDF file at the source link below.
Source: 
California v. McNeal (Supreme Court of California, 7/9/2009)
While I have some skepticism regarding DUI enforcement, I have geometrically more whenever defense attorneys use the word ‘science’.
I’d be rather simple for a research lab to compare breath readings with blood test readings. I assume these studies exist and I assume our fearless legislators know about them.
I may be a naive ass on this, but skepticism about breath tests seems like foil hat science to me.
It should be necessary–and easy–to prove impairment.
I would love it if there were a simple, reasonably priced, reasonably accurate personal breathalyzer, so that people could determine whether they were safe to drive before leaving the restaurant or bar. Perhaps restaurants should have these if they’re not inexpensive.
A quick Google for “personal breathalyzer” brings up this site:
http://www.mypersonalbreathalyzer.com/
For a pretty accurate personal breathalyser, try the Alcoscan AL-7000. Bit more expensive than the average unit, but it’s also meant to be the most reliable ‘cheap’ unit around. It has a replaceable sensor that does not need to be calibrated. I own one and would say it’s pretty accurate after testing with 1 drink, 2, etc. Accuracy is -/+ 0.01 BAC, so if it shows 0.03 or under and I have a clear head I will drive (limit is 0.05 here).
Be aware that cheap breathalysers are wildly inaccurate. Yours will not measure up to what the police use, and the police have the final say.
“But Your Honour, my $29.95 breathalyser said I was under the limit” won’t wash.
Every cheaper system uses a MEMS sensor, whereas the police units have an actual fuel cell to measure the alcohol.
The California decision is actually rather tardy. Other states, including Wisconsin, arrived at the same basic holding almost a decade ago.
That said, the California ruling is plain wrong. Since alcohol in the breath does not cause impairment – only blood alcohol does that – the only theory on which measuring breath alcohol as evidence of impairment is if it does, in fact, correlate to blood alcohol level. Allowing a defendant to prove the conceded and established scientific fact that the relationship between breath and blood alcohol levels extends over a wide range is doing no more than allowing the truth into evidence. Precluding this as a defense to the per se charge is simply making it a crime to fail a test, rather than a crime to do something illegal.
This is what we get with judges who are much more concerned with the next election than with justice. The Mothers Against Drunk Driving and other lobbying groups have these “judges” petrified, as do police groups who also wield a great deal of political power.
We always see judges running for re-election as “tough on crime.” Seldom do you see a judge pointing with pride to a record of having protected the constitutional rights of the citizens.
People fail to appreciate the ultimate tragedy of such decisions as that of the California Supreme Court. It isn’t just that an individual who is really innocent is unjustly convicted. It is also that guilty people will escape conviction. The partition ratio cuts both ways – it can understate blood alcohol, as well as overstate it.
Validating tests which are acknowledged to be massively inaccurate, simply because it’s politically expedient to do so, does not serve the ends of justice for either the accused or the citizenry.
Wait, people are actually accused of DUI solely based on the results of a breathalyzer? I thought those things were used only as a preliminary test – those under the limit would be let go while those over would be taken to an actual mini-lab – in a police station or a mobile one in a police van – where their blood will be sampled and the actual level of alcohol in their blood determined.
The California Supreme Court is not a court that will let facts get in the way of their un-sound judgement…
Justice Carol A. Corrigan wrote: “2100-to-1 ratio overstates the actual amount of alcohol in his blood. For someone with an extremely low ratio of 1100 to 1, for example, use of the 2100-to-1 partition ratio would overstate blood-alcohol content by almost 50 percent.”
Even if I were drunk, I would realize that the above statement should be that the partition ratio would overstate BAC by almost 100%, not 50%.
I wonder if the woman can balance a checkbook?
Mattell should make a Lawyer “Math is hard” Doll.
This is what we get with judges who are much more concerned with the next election than with justice. The Mothers Against Drunk Driving and other lobbying groups have these “judges” petrified, as do police groups who also wield a great deal of political power.
I don’t know if this is it. Ontario has very strict laws about drunk driving and our judiciary is not elected.
The reason we have things like breathalyzers is a) they’re much less intrusive than attempting a roadside blood taking, and b) they’re good enough for getting people off the road. The people who are a concern, and whom programs like this are designed to stop, are the people who wouldn’t know they’re impaired to start with.
If you blow a warning-eligible level, I’d be glad for the police to get you off the road in the short term, even if you “can handle it” or “only test by sample at 0.04 BAC”. Whether you’re charged or not is kind of secondary.
If nothing else, breathalyzers should be a prelude to a blood test. Fail the breathalyzer and you’re automatically down a few cc’s to determine exactly how drunk you are. In that light, there’s nothing wrong with them being set to an overly conservative limit.
Taylor blasted the decision as irrational
From my reading, the decision seems very rational. The irrational part is the law that assigns an arbitrary assumption of BAC to the breath sample. Note that the court did leave open the right of the defendant to challenge the breathalyzer against the DUI charge. Does anyone know whether driver’s in CA have the right to demand a blood test?
If you believe, as I do, that courts should interpret the law and not try to remake them as they see fit, this is a good decision. I just find it hard to believe that such a thing happened in CA; perhaps Rose Bird really is dead…
EEGeek:
If you believe, as I do, that courts should interpret the law and not try to remake them as they see fit, this is a good decision.
+1.
The California legislature should dis-employ the lawyers by just criminalizing BREATH-alcohol content. Replace ‘Blood’ with ‘Breath’ in the current law.
Problem solved.
I agree that it sounds like the correct interpretation of a silly law. That said, I believe that in California you have the right to demand a blood test when accused/arrested for DUI. I know that you can refuse a blood test, but that can be used against you and would certainly prevent you from arguing the validity of the breath test.
If nothing else, breathalyzers should be a prelude to a blood test
Blood tests violate the 5th amendment.