Alcohol breath odor is the most frequently cited observation by US police officers in DWI and other alcohol related traffic offenses. Usually, the strength of the odor is categorized as “strong.” Police officers frequently use the presence or absence of an alcohol breath odor for decisions on proceeding further into sobriety testing after a DWI stop.
A study (Southern California Research Institute and Insurance Institute for Highway Safety) employed 20 experienced officers as observers to detect an alcohol odor from 14 subjects who were at blood alcohol concentrations (BACs) ranging from zero to 0.130 g/dL. Over a four hour time period, each officer had 24 chances to place his nose at the terminal end of a six inch tube through which the subjects blew. The subjects were hidden behind screens with a slit for the tube to prevent any cues but odor cues.
Under these conditions, odor was detected only 2/3s of the time for BACs below 0.08 and 85% of the time for BACs at or above 0.08%.
After food consumption, accuracy declined even further. Officers were unable to recognize whether the alcohol beverage was beer, wine, bourbon, or vodka. Odor strength estimates were unrelated to BAC levels. Estimates of BAC level failed to rise above random guesses. These results demonstrate that even under optimum laboratory conditions, breath odor detection is unreliable, which may account for the low detection rate found in roadside realistic conditions.
Bottom line: there is no way to tie the odor of alcohol to a specific blood alcohol concentration or level of impairment. But that won’t stop officers from trying, or at least using that as pretense to further investigate DWI.
If you’ve been charged with a DWI, call Shreveport lawyer J.P. Guidry.