Blew 0.07 BAC, but I don't drink.
March 19, 2010 8:16 AM   Subscribe

I was stopped at a "sobriety checkpoint". The officer said I blew 0.07, and let me go with a "warning". The catch - I don't drink. Haven't had a drink in 20 years. What's going on?

If it matters, the only thing I ate today was a Dannon yogurt and a cheese sandwich, and water.
posted by anonymous to Law & Government (25 answers total) 10 users marked this as a favorite
did you recently brush your teeth or use mouthwash at all?
posted by royalsong at 8:16 AM on March 19, 2010

My guess is user/machine error. I am not sure how often those things are calibrated, or if the officer had taken a course in correctly using one, but at checkpoints like that, those machines see hundreds of uses a night. I am guessing they aren't calibrated after every use.
posted by TheBones at 8:21 AM on March 19, 2010

sorry, didn't realize you were anon. Here's a quote from Wikipedia alluding to ways to get a false reading:

"One of the most common causes of falsely high breathalyzer readings is the existence of mouth alcohol. In analyzing a subject's breath sample, the breathalyzer's internal computer is making the assumption that the alcohol in the breath sample came from alveolar air—that is, air exhaled from deep within the lungs. However, alcohol may have come from the mouth, throat or stomach for a number of reasons. To help guard against mouth-alcohol contamination, certified breath-test operators are trained to observe a test subject carefully for at least 15–20 minutes before administering the test.

The problem with mouth alcohol being analyzed by the breathalyzer is that it was not absorbed through the stomach and intestines and passed through the blood to the lungs. In other words, the machine's computer is mistakenly applying the partition ratio (see above) and multiplying the result. Consequently, a very tiny amount of alcohol from the mouth, throat or stomach can have a significant impact on the breath-alcohol reading.

Other than recent drinking, the most common source of mouth alcohol is from belching or burping. This causes the liquids and/or gases from the stomach—including any alcohol—to rise up into the soft tissue of the esophagus and oral cavity, where it will stay until it has dissipated. The American Medical Association concludes in its Manual for Chemical Tests for Intoxication (1959): "True reactions with alcohol in expired breath from sources other than the alveolar air (eructation, regurgitation, vomiting) will, of course, vitiate the breath alcohol results." For this reason, police officers are supposed to keep a DUI suspect under observation for at least 15 minutes prior to administering a breath test. Instruments such as the Intoxilyzer 5000 also feature a "slope" parameter. This parameter detects any decrease in alcohol concentration of 0.006 g per 210 L of breath in 0.6 second, a condition indicative of residual mouth alcohol, and will result in an "invalid sample" warning to the operator, notifying the operator of the presence of the residual mouth alcohol. PBT's, however, feature no such safeguard.

Acid reflux, or gastroesophageal reflux disease, can greatly exacerbate the mouth-alcohol problem. The stomach is normally separated from the throat by a valve, but when this valve becomes herniated, there is nothing to stop the liquid contents in the stomach from rising and permeating the esophagus and mouth. The contents—including any alcohol—are then later exhaled into the breathalyzer.[16]

Mouth alcohol can also be created in other ways. Dentures, for example, will trap alcohol. Periodental disease can also create pockets in the gums which will contain the alcohol for longer periods. Also known to produce false results due to residual alcohol in the mouth is passionate kissing with an intoxicated person. Recent use of mouthwash or breath freshener—possibly to disguise the smell of alcohol when being pulled over by police—contain fairly high levels of alcohol."
- Wikipedia
posted by royalsong at 8:23 AM on March 19, 2010 [4 favorites]

Apparently low blood sugar can cause a false positive, as mouthwash and smoking. Given how little you ate I'd suspect it's hypoglycemia though.
posted by opsin at 8:26 AM on March 19, 2010

I don't know the whys, but I would let the police know about what happened. They probably won't do anything, but since that is just .01 off from legally drunk in many states, it's kind of scary that someone who hasn't had a sip to drink in years is blowing almost legally drunk.

In some science class I took in college years ago, we did an experiment where people used mouthwash and blew in breathalyzers. People who had used the mouthwash recently sometimes blew over the limit. The prof said that certain chewing gums could also produce false positives because they have (I think?) sugar alcohols in them.
posted by ishotjr at 8:35 AM on March 19, 2010 [1 favorite]

Diabetes can also trigger a false positive on Breathalyzers.
posted by WinnipegDragon at 8:35 AM on March 19, 2010

You might want to let them know--there have recently been major problems in DC with inaccurate breathalyzers.
posted by sallybrown at 8:36 AM on March 19, 2010

There are tons of things that can cause false readings on those things: mouth alcohol (maybe from mouthwash, as mentioned above), contaminated mouthpiece, RFI interference, test/calibration solution re-used too many times, cop thought you'd been drinking but couldn't get a clean read so he lied to you to make you sweat, etc. I wouldn't think twice about it.
posted by hayvac at 8:37 AM on March 19, 2010

Assuming you are not a type 1 diabetic, it's unlikely that you were hypoglycaemic enough for ketoacidosis to cause a false reading. If you did have ketoacidosis , you would have noticed it (i.e you wouldn't be driving around in your car, you'd be feeling really ill and puking a lot).

My money is on a mis-calibrated breathalizer and/or mouthwash.
posted by EndsOfInvention at 8:37 AM on March 19, 2010

There are lots of ways this could have happened. The most likely reasons are: the officer tampered with the machine, the machine is miscalibrated, or simply that he was lying.
posted by Optimus Chyme at 8:42 AM on March 19, 2010 [4 favorites]

The prof said that certain chewing gums could also produce false positives because they have (I think?) sugar alcohols in them.

This actually happened to me.
posted by phaedon at 8:51 AM on March 19, 2010

The prof said that certain chewing gums could also produce false positives because they have (I think?) sugar alcohols in them.

I hadn't thought of that, but xylitol and sorbitol are all sugar alcohols. I'd never considered that that would mean they could set off a breathalyser. Breathalysers really are a bit shit then...
posted by opsin at 9:16 AM on March 19, 2010

I work with a simple "pocket" breathalyzer at work all the time. (It's the AlcoSensor III if you care to look it up for comparison. I'm in research, not a cop)

The easiest way I could think of to generate that high of a reading on a sober person is to have a drunk person blow into it, then forget to reset and clear the chamber before the sober person blows. The reading could return to zero, but there could still be residual alcohol in the chamber, which gets blown through again by the sober person. Completely basic, but if you're testing hundreds of people a night, chances are you get sloppy once or twice and forget to reset it. This wouldn't matter until you forgot to reset after someone with a high BAC.
posted by slow graffiti at 9:21 AM on March 19, 2010

Acid reflux, or gastroesophageal reflux disease, can greatly exacerbate the mouth-alcohol problem.

I've had GERD for years and never knew that. ta Royalsong. Hopefully it's a fact I'll never need to recall...
posted by sodium lights the horizon at 9:59 AM on March 19, 2010

That may be so, but how many people can legitimately claim this set of facts? I'm not doubting the veracity of your story by any means - but how many people could make the same claim? If I'm a cop (I'm not), most excuses of 'I don't drink' don't get past my BS detector. The more passionate your reasoning, the more likely you are to get stopped or pulled over for the more thorough sobriety test.

There's any number of reasons - and factors - into a false positive reading. There's also a human element to these things - and trying to tell a cop he's wrong is not a road I'd want to go down. If you're going to complain to someone, make sure that it's someone unlikely to find you at a future sobriety checkpoint.

Just my two cents :)
posted by chrisinseoul at 10:03 AM on March 19, 2010

Some kinds of breath mints are reputed to be picked up by the machines. The apocryphal story was that someone chewed a couple of peppermit tic-tacs just before a test, and it resulted in a reading for a blood level that should have been fatal.
posted by Chocolate Pickle at 10:06 AM on March 19, 2010

he could also be fucking with you. whatever the reason, you should mention this to your police department.
posted by randomstriker at 10:11 AM on March 19, 2010 [1 favorite]

My experience with one police officer was this: after I was pulled over in my brand new Civic (about 10 years ago), the officer came up to my window. I gave him my license, insurance and registration. He returned to his cruiser, and came back. I asked him what the problem was. He asked me if I had ever gotten a ticket before. I told him, truthfully, "Never." "Really?" he asked, incredulous. Then he told me my rear license plate light was out, but he was letting me off with a warning.

My license plate light was not out, and in 10 years of driving the car, never ever, ever, ever went out.

My point is, sometimes police officers lie about little things, and then "let you off with a warning."

On the other hand, about a year before that, I was driving a pickup truck down PCH, and was told by a police officer that my tail light was out. However, my tail light was indeed out. She also let me off with a warning; not even a fix-it ticket. I fixed everything that night, and would have sent her a thank you card for being so awesome had I thought of it.
posted by jabberjaw at 10:59 AM on March 19, 2010 [1 favorite]

I just wanted to clarify some of the claims here about diabetes. If someone is hypoglycemic (low blood sugar), they may have symptoms of being drunk (confusion, unsteadiness, anger) but hypoglycemia does not lead to ketoacidosis, despite information that can be found on the internet. It is only hyperglycemia (high blood sugar) that, if somewhat prolonged, can lead to ketoacidosis and therefore apparently trigger a breathalyzer.
posted by chinston at 11:05 AM on March 19, 2010 [1 favorite]

Once in high school health class a cop came in to demonstrate teh breathalyzer. He picked a student and performed the test. Teh student failed. She was not drunk, but she was an insulin dependant diabetic.

Just in case the cop wasn't lying to you, if in the future you ever find law enforcement trying to get you on a charge related to being drunk, request a blood test.
posted by WeekendJen at 11:27 AM on March 19, 2010 [1 favorite]

The officer said I blew 0.07, and let me go with a "warning".

The officer is likely aware of all the limitations of the test mentioned above, so when the number came back like it did, it didn't correlate with any of the observed behaviors he was seeing in you -- you likely weren't slurring, stumbling, combative, loopy, etc.

Just in case the cop wasn't lying to you, if in the future you ever find law enforcement trying to get you on a charge related to being drunk, request a blood test.


But keep in mind that the time delay won't be such that you'll sober up between the time they arrest you and when they find a nurse. They'll take your blood, run the test, and then match up the alcohol level with known average rates of metabolism, i.e. "He blew X percent now, so that means 60 minutes ago when he was driving, he was between Y and Z percent."

Can't tell you how many people I know think the hour-or-so delay between arrest and blood test will be enough time for them to pass safely under the impairment level.
posted by Cool Papa Bell at 12:10 PM on March 19, 2010

My guess is the office was bullshitting you. Either he had a hunch you were going to be drinking and wanted to discourage you, or he does that to almost everyone using it as some form of deterrent.
posted by I am the Walrus at 2:28 PM on March 19, 2010

An old coworker's 16 year old daughter blew .03 with the mouthwash thing - since legally it's 0 for people on learner/probationary licences they waited around for 20 minutes and did it again.
posted by geek anachronism at 4:01 PM on March 19, 2010

I heard a rumor that, with NO alcohol consumption whatsoever that day, but having using mouthwash, say, 30 minutes before getting into the car and blowing into an ignition interlock device, can make you fail. Of course, in many cases (in this one, anyway), "fail" is anything above .02, NOT .08.

Just something I, uhhh . . . heard about once. No personal knowledge or anything.

(I can't whistle, but if I could, I'd be doing so in a most innocent manner right now.)
posted by CommonSense at 4:24 PM on March 19, 2010

Hand sanitizer, recently used by either you or the cop, is yet another source of possible false positives.
posted by granted at 10:16 PM on March 19, 2010

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