Some people in Illinois who are on low-carb diets or who have other medical conditions may have false-positive results for a blood alcohol content that is over the legal limit on some types of breath test. A Texas attorney was able to get his client’s case dismissed because the man was in ketosis at the time he took his breath test.

Ketosis, which is a state that results from low-carb diets, causes the liver to produce acetone. Acetone can be converted to isopropyl alcohol when it is breathed out, and some argue that certain types of breath tests cannot tell the difference in this and ethanol alcohol. Self-checking testers that use semiconductor technology are probably not reliable, but the portable models that police usually have use fuel cell technology. Manufacturers say these are accurate, but the Texas attorney says no peer-reviewed studies have proven they can distinguish ethanol from isopropyl. Furthermore, one study was published in 2006 that examined a man who could not start a company vehicle that required a breath test using fuel cell technology. The man was on a low-carb diet. Diabetes and acid reflux could also create false positives.

However, devices that use infrared spectroscopy, usually available back at the police station, do not have this issue. In some cases, a person might also be able to request a blood test.

People who are facing DUI charges may want to discuss the issue with an attorney. A DUI conviction can have such repercussions as license suspension or revocation, fines or jail time. In addition to the legal consequences, conviction for a DUI may affect the careers of some people. An attorney might examine whether the charge could be the result of a false positive or an inaccurate report by law enforcement. The attorney may also consider whether the person’s rights were observed when being taken into custody.