Interfering Subtances Can Push You Over the Legal Limit

Posted On July 18, 2023 Charles Ramsay

Last week, I told you I’d share the mind-boggling analysis from a recent Government data practice request I made to the BCA breath alcohol lab. 

Here it is: In ~25% of cases near the 0.16 legal threshold, interfering substances (like acetone and isopropanol) pushed drivers over the legal limit! This means if you have a breath test result ending near 0.16, you have a 1 in 4 chance of actually being under the 0.16 legal threshold.

A few weeks ago, I requested raw data from the state breath alcohol lab regarding the raw filter values for breath samples that ended near the 0.16 legal threshold and asked former BCA scientist Aaron Olson to analyze the data. 

What he found blew my mind.

The results of the analysis are significant because, at the 0.16 level, you’ll be slapped with additional criminal penalties and a longer license driving suspension – including no driving unless you install an ignition interlock device (a disabling device that won’t let you start your car unless you demonstrate no alcohol on your breath – a truly embarrassing situation if you have passengers or are seen by neighbors or other drivers!).

What are interfering substances?

Recently, diets like keto, paleo, and low-carb have become more popular. While these diets might work for weight loss, they are terrible for breath alcohol testing.

As your body burns fat, it produces acetone and isopropanol as byproducts. 

Image credit: Jones AW, Rössner S. False-positive breath-alcohol test after a ketogenic diet. Int J Obes 2007; 31: 559–561.

The fact is, these substances are a normal part of human metabolism. The problem is, they look very similar to ethanol — the alcohol found in beer, wine, and liquor.

The problem with the DMT and interfering substances

There’s a big problem with the DMT. In 2012, the BCA lab shut off the fuel cell. It was an important quality control that helped flag interfering substances like acetone and isopropanol. When the state shut it off, they left only one quality control behind: the infrared filters. 

But the filters only flag once interfering substances reach a certain threshold. If the interfering substance is below the threshold, the DMT won’t flag it. This means that you could have a normal substance on your breath (as the result of fat loss) that pushes you over the legal threshold due to no fault of your own.

Image credit: Aaron Olson.

Get a fair shot at trial

Were you on a low-carb diet when you took the state’s breath test? You may have been pushed over the legal limit due to no fault of your own. If you’ve been a victim of the state’s shoddy breath alcohol machine, call Ramsay Law. We use science and the law to get you results.