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Breathalyzers: How They Work and Why They Are Inaccurate

Posted on in Traffic Offenses

Breathalyzers: How They WorkNearly everyone in America is familiar with the fact that it is illegal to drink and drive. Doing so violates a state's driving under the influence (DUI) law. However, not very many have considered the intricate issue of how law enforcement can effectively determine whether someone is “under the influence” of alcohol. That police use breathalyzers is common knowledge, but how do they work?

How Alcohol Gets Into Your Blood

When you drink an alcoholic beverage, it gets swallowed down your throat and makes it to your stomach. From there, the liquid passes into the intestines. Throughout its travels inside your body, the alcohol seeps through the inner linings of your organs and into your bloodstream. Once in your bloodstream, the alcohol flows with your blood through your veins and arteries.

The amount of alcohol in your blood is your blood alcohol content (BAC) and is measured as a ratio of milliliters of alcohol per 100 milliliters of blood. But this only gets us to alcohol in your blood. How does a breathalyzer work when it does not take a sample of your blood?

The Science of Breathalyzers

When your alcohol-laden blood passes through your body, one of the places where it stops is your lungs. While your blood passes through your lungs, some of the alcohol that it is carrying stays there. Chemically, the amount of alcohol that gets left behind is directly proportional to the amount of alcohol in your blood – the same amount of alcohol that is in one milliliter of blood is also in 2,100 milliliters of breath. Because of this, the amount of alcohol that is on your breath when you exhale mirrors the amount of alcohol in your blood.

This chemical process is what allows police to use a sample of your breath to determine how much alcohol is in your bloodstream.

An Imperfect Process

Unfortunately, like any scientific process, this one is difficult to replicate precisely in the field. Whenever you take a breathalyzer test after being pulled over, there are numerous things that can go wrong with the reading. Chief among them is the fact that the breathalyzer takes the sample of breath from your mouth, not directly from your lungs: Latent alcohol that has been absorbed by your cheeks and gums can increase the BAC reading from a breathalyzer. Even this small increase can turn a BAC reading below the legal limit in Illinois' DUI law to one above it.

Let Our McHenry County Defense Attorneys Help You

If you have been pulled over, arrested, and charged with driving under the influence (DUI) in northern Illinois, you need a DUI-defense attorney to help you combat the charge in court. Contact the dedicated Crystal Lake DUI attorneys at Botto Gilbert Lancaster, PC online.

Sources:

http://electronics.howstuffworks.com/gadgets/automotive/breathalyzer.htm

http://www.ilga.gov/legislation/ilcs/fulltext.asp?DocName=062500050K11-501

Illinois State Bar Association State Bar of Wisconsin Crystal Lake Chamber of Commerce Illinois Trial Lawyers Association McHenry County Bar Association
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