Can an extreme weight loss diet affect breath test results in a DUI case?

Recently I was asked this question in a criminal defense forum….Can an extreme weight loss diet affect the breath test results in a DUI case.  Specifically can it lead to a higher breath test result that is false?  The answer is absolutely it can and with all the fad diets out there this defense should not be discounted when representing a driver accused of a DUI.

Now I’m not going to get into the real specifics of this science.  As I’m just a Seattle DUI Attorney and not a Physician or expert regarding this issue.  But I am familiar with the basics.  Basically when a person is on a low carb or extreme diet the body will turn to ketones for energy rather than glucose produced by carbohydrates.  Ketones are water soluble products of fat metabolism.  The idea behind a diet is to burn stored fat which in turn produces these ketones.

The interesting issue with these ketones is their chemical composition is similar to isoproponal which is a type of alcohol.  Whatever ketones that don’t get used will exit the body.  And you guessed it a portion will exit through an individuals breath.  Unfortunately if you get arrested for a DUI here in Seattle chances are you provided a breath test sample with the Datamaster.  This machine cannot tell the difference between isoproponal and ethyl alcohol which is the alcohol found in beer, and liquor.

So what happens.  The machine detects the isoproponal and provides a false reading that is higher than the actual alcohol level and it is then used against the driver in a prosecution for DUI.  This is a very brief overview of how this process works, but nevertheless you get the idea.

Another interesting note with a driver who is on an extreme diet.  Typically they are tired, slow moving, etc.  Exhibiting all the classic signs of alcohol impairment that are then misinterpreted by law enforcement and the prosecution in a DUI case.  But that is another issue.

If you have been recently arrested for a DUI in Seattle or in Washington State and you were taking part in an extreme diet or taking diet pills.  It is important to speak immediately with your DUI Attorney about how this could have caused a false reading in the breath test results.

About the author:  Matthew Leyba is a DUI Attorney in Seattle.  He is the firm owner of Leyba Defense PLLC, a boutique criminal and DUI law firm located in Seattle.  He has been repeatedly recognized as one of the best DUI Attorneys in Seattle by the Seattle Met Magazine’s annual “best of” edition.  He is also the highest rated DUI Attorney in Seattle by