When I see a breath test being given, I always hear, “keep blowing” or “blow harder”. These commands make the subject keep blowing long after they need to, and it helps the police insure the breath test is higher than the true BAC. Especially in close cases, to the legal limit, or the enhanced limit, it can result in the difference between a not guilty and a guilty verdict. The police have no concern about inflating the number when they are rewarded for making more DUI arrest and citations. But we know this practice is wrong. It’s not just anecdotal, but based on a study of this phenomenon. In Varying Length of Expirational Blow and End Result Breath Alcohol, found in the virtual library here: https://drive.google.com/file/d/0BxbLCAZZvzl3eVV1Q0pFb19ZM1U/view?usp=sharing
Western Michigan conducted a study to determine the impact of this phenomenon. What they found, is exactly what we have been saying, “the longer you blow, the higher you go”. When the police manipulate the results to increase the reading, it is wrong. With this study, the practitioner can show how the police do it, and why it matters. Next time the officer makes your client blow longer, make sure the jury knows the result is unreliable. Let them send a message to the police to conduct the test properly and reliably, so next time, they aren’t the ones sitting at the defendant’s table.