In most situations, however, alcohol consumption does not immediately relate to intoxication. Remember, it is not illegal for most drivers aged 21 and above to drink and drive if they do not have alcohol restrictions on their licenses. It is only considered illegal to be intoxicated or impaired while operating a motor vehicle.
The estimated strength of alcoholic odor is typically unrelated to the driver’s actual BAC levels. The detection of an individual’s BAC by basis of odor is far from accurate. It is very possible for motorists to be impaired or intoxicated without producing sufficient odor to alert an officer. Ethanol, after all, has no scent.
All that can be gathered from the odor of alcohol on the driver’s breath is that he or she likely consumed an alcoholic beverage recently. It does not provide enough evidence that he or she had enough to be under the influence or have a BAC of .08 or higher.
The Insurance Institute for Highway Safety supported a scientific study that determined that the odor of alcohol is not a reliable and sufficient probable cause to request a chemical test or arrest a driver for DWI.
Given the sheer difficulty of estimating an individual’s BAC from the strength of his or her alcohol odor, using odor as a form of evidence should definitely not be relayed to a jury in a DWI case, and should not even be used to back probable cause for an arrest.