These days, a lot of people are on the keto diet, a low-carb diet advertised to encourage weight loss. The diet puts your body into a state called “ketosis,” where the liver begins to break down fat to fuel the body. Acetone, a byproduct of ketosis, is released through the breath in the form of isopropyl alcohol. This is different from ethanol, which is the type of alcohol people drink. The question is, can breathalyzers tell the difference?
It’s not clear. According to a professor of forensic technology from Sweden’s Linköping University explained to Men’s Health recently that cheap models probably can’t tell the difference. The head of a breathalyzer manufacturer agreed. The models that people buy on their own to self-monitor their blood alcohol content are somewhat different from those used by police. A metal film inside the device merely measures the number of alcohol molecules present.
The head of the breathalyzer company interviewed insists that police models can tell the difference between the two kinds of alcohol. These rely on fuel cells, and the technology can supposedly differentiate between isopropyl and ethanol alcohols. However, a defense attorney interviewed for the story pointed out that he has seen no peer-reviewed studies showing that to be the case.
Moreover, people in ketosis who have also been drinking may have both types of alcohol in their breath. There is little evidence that police breathalyzers would read only the ethanol content in such a situation.
It’s also unclear whether ignition interlock devices can differentiate between the two types of alcohol. There have been instances in which people were unable to start their vehicles because an interlock misread the isopropyl alcohol on their breath as ethanol. Interlocks generally prevent the vehicle from starting if the person’s breath alcohol exceeds 0.02 percent.
Could ketosis actually cause a false positive breathalyzer test?
It’s theoretically possible, especially considering there are several different brands of police breathalyzer being used. However, this might only occur if the driver’s blood alcohol level was close to the limit anyway. The amount of isopropyl alcohol created by ketosis probably is not sufficient to reach 0.08 percent, the legal limit in Iowa and most states.
If you suspected that the keto diet was responsible for an undeserved 0.08 reading, you could ask for a blood test. And, in many states, breathalyzer tests are considered preliminary and must be backed up by an infrared spectroscopy test that is given at the police station. Such tests are likely to be more accurate at differentiating isopropyl from ethanol alcohol.
If you are concerned your OWI breath test was inaccurate, contact an experienced criminal defense attorney right away.