The point of using a hand sanitizer is not just to wash your hands, but to kill germs on your skin. To accomplish this purpose, many hand sanitizers use ethanol as their active ingredient. As you may already know, ethanol is also the active ingredient in alcoholic beverages. But if a police officer pulls you over on suspicion of drunk driving and ends up administering a breath test to you, can an alcohol-based hand sanitizer trigger a false positive breathalyzer result—even if you haven’t had anything to drink? The answer in some cases is, “Yes.”

Before we go into the details of how this can happen, we should make clear how it can’t. To begin with, these kinds of false positive readings do not involve you consuming the hand sanitizer. Although cases have been reported of intoxication from ingesting hand sanitizers, these almost invariably involve small children who swallow the product by mistake. In fact, the scenario we are contemplating doesn’t have you using the hand sanitizer at all. It is the police officer’s usage that can lead to the erroneous result.

Law enforcement is often a “hands-on” occupation. To protect themselves from the possibility of catching something contagious from people they interact with, some police officers are quite fastidious about keeping their hands clean. They use hand sanitizers frequently, including sometimes before administering a breathalyzer test. Interestingly, however, the breathalyzer devices commonly used by police today are sensitive enough that they can detect not only ethanol on your breath, but also ethanol that is evaporating from the officer’s hands after he or she has used a hand sanitizer.

Studies dating back to 2013 and even earlier have shown that this is more than a theoretical possibility. And the sanitizer-based reading can be high enough to make it look like you’ve drank enough alcohol to put you well over Oklahoma’s .08 limit for blood alcohol content. Indeed, according to a recent study conducted by the American Journal of Infection Control, the false positive test result can register a reading as great as .15—nearly double the legal limit.

Factors that can influence a hand sanitizer-based breathalyzer result include:

• How much sanitizer the officer applies to his or her hands. The more that is used, the stronger the breathalyzer reading can be.
• How much time has elapsed from when the officer applied the hand sanitizer to the administering of the test. A false positive reading can still register for up to three minutes after application.
• Whether the officer puts on gloves after applying the hand sanitizer. While glove use can significantly reduce the chance of the breathalyzer picking up the ethanol on the officer’s hands, it does not completely eliminate it.

So does this mean that, even if you have been drinking alcohol, you can rest easy when you see the officer putting on hand sanitizer? The thing to keep in mind here is that the police are well aware of these same studies, and their training can include measures to minimize the chance of a false positive reading. These can be based on common sense measures such as not using a hand sanitizer before the breathalyzer test, or using a modest amount and waiting for more than three minutes after such use, or combining such a delay with glove usage.

In short, whether you can use the “hand sanitizer defense” if you are accused of DUI depends heavily on the facts of your case. This is something that your DUI defense attorney can analyze on your behalf, along with other possible challenges to the technology being used against you by law enforcement.