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Breathalyzers — and why they don’t work

Posted by Lawrence Taylor on October 17th, 2004

So what did I mean in my earlier post by "unreliable breath machines" and "passing laws against science"? Here’s just one of many examples… The computers inside Breathalyzers actually multiply the amount of alcohol in a DUI suspect’s breath sample 2100 times to get the blood alcohol concentration ("BAC"). This is because it is programmed to assume that the suspect has 2100 units of alcohol in his blood for every unit of alcohol in his breath. This is called the "partition ratio". But this ratio is only an average: actual ratios vary from as low as 900:1 to as high as 3500:1; if individual ratio is different, the BAC result will be different.

Translation: If a suspect has a true BAC of .06% ("not guilty") and a partition ratio of 1300:1, for example, the machine will give a result of .10% ("guilty"). Convicted by a machine. His crime? He was not average.

Well, when juries hear this kind of evidence, they tend to return "not guilty" verdicts. This did not sit well with MADD’s and prosecutors’ lobbyists. The result: in California and other states, drunk driving laws were changed by adding "Percent, by weight, of alcohol in a person’s blood is based upon grams of alcohol per 210 liters of breath". In other words, the law no longer cared what the actual amount of alcohol was in your blood: it was legally (not scientifically) presumed to be 2100 times what is in your breath — even though we know it is not.

The conservative California Supreme Court later found the new DUI law constitutional in People v. Bransford. But a dissenting Justice pointed out the obvious: "The majority…has on its own created the new crime of driving with alcohol in one’s breath". (Justice Joyce Kennard, 8 Cal.4th 894)

Result: today, defense attorneys are prohibited from mentioning anything about partition ratios to a jury. Scientific truth has been banned from the courtroom. And the conviction rate in drunk driving cases has risen dramatically.

This entry was posted on Sunday, October 17th, 2004 at 11:23 am and is filed under Duiblog. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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  1. […] The problem is that “breathalyzers” are designed to assume that the breath sample contains alcohol which has been swallowed and then metabolized by the body before being diffused into the lungs. As I mentioned in an earlier post (”Breathalyzers — and Why They Don’t Work“), they are further designed to assume that there are 2100 units of alcohol in the blood for every unit measured on the breath. So the breathalyzer�s computer mistakenly multiplies the alcohol measured from the asthma inhaler 2100 times. In other words, a very tiny amount of alcohol in the lungs from the inhaler mist can have a very large effect on the machine�s reading. […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 6, 2006 @ 11:22 am

  2. […] One of the many problems with breath machines is that they cannot tell the difference between alcohol coming from the lungs and alcohol which is already in the mouth or throat. This problem is referred to as “mouth alcohol”, and is particularly troublesome because, believing it to be alcohol from the lungs, the breath machines will incorrectly multiply the detected alcohol by 2100 times (see my earlier post, Breathalyzers — and Why They Don’t Work). […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 6, 2006 @ 11:49 am

  3. […] I’ve written a number of times about the inaccuracy and unreliability of breathalyzers (see, for example, ” Breathalyzers — and Why They Don’t Work“, “Why Breathalyzers Don’t Measure Alcohol“, “Breathalyzers: Why Aren’t They Warranted to Measure Alcohol?”). For those of you who still believe that these machines are accurate, consider the following news article: MINNEAPOLIS (January 31, 2005) – Before he went to law school, Brian Eddy worked at a firm that often handled drunken-driving cases. He noticed that many of the clients snagged for driving under the influence made the same doleful observation: “I had no idea I was that drunk.”It occurred to Eddy that there must be a way to quickly screen one’s blood-alcohol level after a few drinks. He bounced the idea off a childhood friend, and the two ponied up $100 from their savings accounts to start a business. Before he knew it, Eddy was not only a budding lawyer but a budding entrepreneur.Fast-forward six years: Eddy is now the chief executive of Q3 Innovations, an Eagan, Minn., company that has successfully marketed the Alcohawk ABI digital breath alcohol screener to retailers Sharper Image and Target. He has even bigger retailers on his radar, including Best Buy, Circuit City and Radio Shack…. Eddy points out that….the U.S. Department of Transportation has cleared the device for use by law enforcement professionals, a market Q3 Innovations has yet to aggressively tap. [Emphasis added]”The reason people are skeptical is because there is a lot of junk on the market,” Eddy said of the competition. “It’s a perception that we have to overcome.” How accurate do you think this “budding” lawyer-entrepreneur’s product is? Would you want to face arrest and prosecution for DUI because of its reading? And just how demanding could the Department of Transportation’s standards be? Note: Most states rely upon the U.S. Department of Transportation’s list of approved breath testing instruments as the standard for admissibility as evidence in court. Young Brian Eddy’s pocket-sized gizmo, available at any Target store, is legally good enough to sustain a criminal conviction for drunk driving. As I commented in an earlier post, it’s “close enough for government work“. (Thanks to Kathleen N. Carey of Phoenix, Arizona) Share: […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 6, 2006 @ 11:54 am

  4. […] I’ve written in past posts that the “DUI Exception to the Constitution” for roadblocks has been badly abused. Specifically, police are increasingly using these ineffective and intrusive roadblocks to issue unrelated citations and increase governmental revenue…. Police say DUI Checkpoint was a Success […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 11, 2006 @ 3:19 pm

  5. […] In recent days I’ve talked about how DUI roadblocks (or to use the more politically correct term, “sobriety checkpoints”) are ineffective and violate the Fourth Amendment but have nevertheless been authorized by the U.S. Supreme Court because the intrusion on citizens’ privacy was outweighed by the “grave and legitimate interest in curbing drunken driving”. And I pointed out that, inevitably, law enforcement was increasingly abusing the procedure to gather information about citizens, conduct dragnets for non-DUI offenses and raise money for local government. In the following news story about a weekend “sobriety checkpoint” in North Carolina, notice the emphasis in the opening paragraph on the minimal arrests for DUI — and the real objective as evidenced by the list of total arrests in the last paragraph: Area law enforcement officers levied charges against drunk driving suspects Friday at a checkpoint at the intersection of North Raleigh Street and Meadowbrook Road. Rocky Mount police said two vehicles were seized from drivers charged at the checkpoint during a joint effort with area law enforcement agencies…. Arrests resulting from the checkpoint included the following charges: Driving while intoxicated, three; alcoholic beverage control violations, three; driving while license revoked, four; no operator’s license, five; fail to carry license, three; seat belt violation, one; expired license plate, three; no insurance, one; unauthorized use of motor vehicle, one; misdemeanor possession of marijuana, one; possession with intent to sell/deliver marijuana (felony), one; felony maintain a vehicle, one; child restraint violation, six; inspection violation, three; careless and reckless driving, two; felony elude, two; fail to stop for lights and siren, one; outstanding warrants, three; commercial motor vehicle regulatory violation, two; resist, obstruct and delay, two. […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 11, 2006 @ 3:23 pm

  6. […] Did you ever wonder how breathalyzers work? There is a website which will give you a pretty fair idea. But first, let’s clear up some confusion…. There are many different kinds of “breathalyzers” — or, more accurately, there are many kinds of breath testing devices. The first of the modern breath testers, manufactured by Smith and Wesson many years ago (yes, that Smith and Wesson), was called the Breathalyzer. Since then, various manufacturers have recognized the growing market and come out with their own models, bearing such names as Intoxilyzer, Intoximeter, DataMaster, AlcoSensor, Alcotest and so on; most of these products have been produced in different model versions, such as the Intoxilyer 4011, 5000 and 8000. To deal with the confusion, the term “breathalyzer” came to be used as a generic term for any breath testing instrument. (To confuse things further, a German company — Draeger — bought the rights to the Breathalyzer brand and have sometimes used that name in some of their models.) Most of these are evidentiary machines — that is, larger machines generally kept at the station whose test results are used in evidence. Others are smaller, handheld units carried by officers in the field; these are less accurate, and are usually used as a field sobriety test to help determine whether to arrest a suspect. The original Breathalyzer operated using a wet chemical method of analysis, employing a disposable glass ampoule of chemicals. Although still occasionally found in law enforcement, this relatively primitive technology was replaced in later machines by infrared spectroscopy, gas chromatography or, mainly in handheld units, fuel cell analysis; a couple of the more recent machines use a combination of infrared and fuel cell. Now that this has been cleared up, you might want to visit the following sites to understand the actual workings of these gizmos: Chemical (the Breathalyzer) Infrared spectroscopy (the Intoxilyzer) Fuel cell (the Alcosensor) Note: Gas chromatography is rarely encountered anymore, as it was primarily used in the discontinued Intoximeter 3000. Note #2: To further understand why these machines aren’t nearly as accurate as law enforcement would have you believe, visit a few of my previous posts: Breathalyzers — and Why They Don’t Work Breathalyzer Inaccuracy: Testing During the Absorptive Stage Breathalyzer Inaccuracy: Post-Absorptive Breathalyzer Inaccuracy….It Gets Worse “Close Enough for Government Work” Why Breathalyzers Don’t Measure Alcohol How to Fool the Breathalyzer Breathalyzers and Radio Frequency Interference Breathalyzers: Why Aren’t They Warranted to Measure Alcohol? Share: […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 11, 2006 @ 3:25 pm

  7. […] The effects of changes in body temeprature from the norm of 98.6 degrees on breath testing has been discussed in an article entitled “Body Temperature and the Breathalyzer Boobytrap”, 721 Michigan Bar Journal (September 1982). If because of illness, for example, the body temperature is elevated by only 1 degree Centrigrade (1.8 degrees Fahrenheit), the 1:2100 breath-to-blood partition ratio used by breathalyzers will be altered so as to produce a 7 percent higher test result. Higher body temperatures will, of course, result in even greater errors. […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — December 21, 2006 @ 12:30 pm

  8. […] explained many of the reasons why breathalyzers are inaccurate and unreliable. See, for example, “Breathalyzers — and Why They Don’t Work“; ”Warning: Breathalyzer in Use“; ”Convicting the ‘Average’ DUI Suspect“; “Why […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — March 12, 2007 @ 9:07 am

  9. […] 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 […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — October 16, 2008 @ 9:19 am

  10. […] case case, the 4th Amendment’s protection against stops by police for no cause. (See "DUI Sobriety Checkpoints: Unconstitutional?") Yet, checkpoints have repeatedly been shown to be considerably less than effective (see […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — October 16, 2008 @ 5:05 pm

  11. […] 2100 figure is based upon the partition ratio in the average human; the actual ratio varies widely from one person to another. This variance […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — October 22, 2008 @ 1:49 pm

  12. […] the machine; malfunctions in the machine; design defects (there are many: see, for example, "Breathalyzers — and Why They Don’t Work" and "Why Breathalyzers Don’t Measure Alcohol"); maintenance and repair […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — October 23, 2008 @ 1:51 pm

  13. […] 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 […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — October 23, 2008 @ 6:30 pm

  14. […] I have called "The DUI Exception to the Constitution". These have included approval of sobriety roadblocks (Sitz v. Michigan); double jeopardy (immediate license suspensions followed by criminal […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — October 23, 2008 @ 6:38 pm

  15. […] Breathalyzers — and Why They Don’t Work Close Enough for Government Work The Mouth Alcohol Problem Breathalyzers: Why Aren’t They Warranted to Measure Alcohol? Driving Under the Influence of….Bread? Warning: Breathalyzer in Use Breath Fresheners and Breathalyzers Diabetes and the Counterfeit DUI Why Breathalyzers Don’t Measure Alcohol Can Body Temperature Affect Breathalyzer Results? The Effect of Anemia of Breath Tests GERD, Acid Reflux and False Breathalyzer Results Driving Under the Influence of….Gasoline? Do Breathalyzers Discriminate Against Women? Breathalyzer Inaccuracy: Testing During the Absorptive State Breathalyzer Inaccuracy: Post-Absorptive Breathalyzer Inaccuracy….It Gets Worse Warning: Smoking Can be Hazardous to Breathalyzer Results How to Fool the Breathalyzer Breathalyzer Manufacturers Won’t Tell How They Work […]

    Pingback by DUI BLOG : Bad Drunk Driving Laws, False Evidence and a Fading Constitution — February 15, 2009 @ 10:53 am

  16. […] What happened? One of the many problems with breath machines is that they cannot tell the difference between alcohol coming from the lungs and alcohol which is already in the mouth or throat. This problem is referred to as mouth alcohol, and is particularly troublesome because, believing it to be alcohol from the lungs, the breath machines will incorrectly multiply the detected alcohol by 2100 times (see my earlier post, Breathalyzers — and Why They Don’t Work). […]

    Pingback by DUI BLOG: Driving Under the Influence of…Binaca? — January 25, 2011 @ 5:27 am

  17. […] Breathalyzers — and Why They Don’t Work Breathalyzer Inaccuracy: Testing During the Absorptive Stage Breathalyzer Inaccuracy: Post-Absorptive Breathalyzer Inaccuracy….It Gets Worse “Close Enough for Government Work” Why Breathalyzers Don’t Measure Alcohol How to Fool the Breathalyzer Breathalyzers and Radio Frequency Interference Breathalyzers: Why Aren’t They Warranted to Measure Alcohol? […]

    Pingback by What Are Breathalyzers, How Do They Work…and Are They Accurate? | DUI Law Blog — May 13, 2012 @ 10:28 am


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