People in Illinois who are on a low-carb diet that has put them into ketosis or who suffer from such conditions as acid reflux or diabetes could cause some types of breath tests for blood alcohol content to give inaccurate results. In Texas, an attorney got DUI charges dropped against a man who was in ketosis but who did not appear to be drunk during field sobriety tests. However, when he took a breath test, the device registered his blood alcohol content above the legal limit.

The problem is that ketosis and other conditions may cause people to breathe out isopropyl alcohol. There is some disagreement about whether some types of breath tests can distinguish between isopropyl and ethanol alcohol. One professor contends that home BAC tests, which use semiconductor technology to detect the number of molecules in a person’s breath, may be unable to distinguish between the two types of alcohol.

The same professor also wrote a paper in 2006 about a man on a low-carb diet who was unable to activate the ignition interlock device on a company vehicle. That device used fuel cell technology. The attorney who defended the man in Texas says there are not peer-reviewed studies that indicate that fuel cell technology can make the distinction although manufacturers say they are ethanol-specific. Devices that use infrared spectroscopy can distinguish between the two.

A DUI conviction can have serious consequences, including license suspension, and people who are facing charges may want to contact an attorney about possibilities for defense. Some other medical conditions or a reaction to medication can make a person appear as though they are intoxicated. An attorney might also examine whether tests were administered correctly or if the person’s rights were violated in the course of the traffic stop or while being taken into custody.