How Can Mouth Alcohol Result in Falsely High BAC?

One of the most common pieces of evidence used in DWI cases are breath tests. While it is not illegal to drive with alcohol in your stomach, it is only illegal if it impairs your ability to drive or if your BAC is at or above the legal limit of .08%.

Thus, the best way to prove a DWI case is to test someone’s BAC.

However, mouth alcohol that +-is a common factor that can throw off a breath test. Since a breath test relies on the amount of alcohol particles in your breath as your breath out, rather than analyze your blood, mouth alcohol can potentially put additional particles into the air, although it doesn’t reflect your BAC. As a result, the test would assume you’re far more inebriated than you actually are.

Typically, when you consume alcohol, it’s out of your mouth relatively quickly—most traces are gone within 15 minutes or so. Yet, there are times when either alcohol ends up back in the mouth, or something else creates mouth alcohol and interfere with the test.

The following are the most common sources of mouth alcohol:

  • Burping – A burp can contain a small amount of alcohol, which can cause a significant discrepancy in breath test results. This is why law enforcement officials are required to perform a 15-minute “observational period” prior to the administration of the breath test. During this period, they are supposed to ensure that you do not burp, hiccup, or vomit. It is quite common for police to sometimes skip this protocol or fail to pay close attention.
  • Mouthwash – Mouthwash, such as Listerine or Scope, is used to cover up the smell of alcohol on their breath. However, mouthwash is made with alcohol. For instance, Listerine has more than 26% alcohol by volume, while Scope has nearly 19%.
  • Heartburn or acid reflux – Certain health conditions can create mouth alcohol. This includes heartburn, acid reflux, and gastroesophageal reflux disease (GERD). Heartburn or reflux produces mouth alcohol because it causes the contents of the stomach to flow back into the esophagus and contaminate your mouth.
  • Medicines – Medicines, such as Nyquil or Tylenol, contain alcohol. Since these cough medicines are syrupy substances, they can leave residue in your mouth. If a type of medication makes you fatigued or woozy, the side effects could be mistaken for symptoms of intoxication.
  • Dental work – If you have braces, dentures, or any other type of orthodontics, these devices can trap food or liquid. So if they trap alcohol, it will affect the breath test.
  • Breath sprays – Similar to mouthwash, some breath sprays contain alcohol.

When mouth alcohol becomes a factor in a DWI case, it can mean that the breath test cannot be considered as evidence, which could potentially in your entire case being thrown out. To know whether mouth alcohol is viable defense strategy in your case, it is wise to speak with an experienced criminal defense attorney immediately.


For more information, contact our Hidalgo County criminal defense attorney at The Law Office of Rene A. Flores PLLC today.

Categories