At some point, you may have wondered, “If it's illegal to drive with a blood alcohol content at or above 0.08%, how can a breath test be used as evidence? It's blood alcohol content, not breath alcohol content."
If you asked a policeman this question, they'd say that blood alcohol content is the same thing as your breath alcohol content. While unlikely, they might even be aware of the science behind it: When you drink, alcohol gets into your bloodstream, but some gets left behind when your blood travels through your lungs and makes its way into your breath when you exhale.
However, while the idea that breath and blood alcohol content are the same thing is a convenient one for law enforcement, it's not entirely true. The reality is that there are lots of ways for your breath alcohol content to be different from your blood alcohol content. This can result in an incorrect BAC reading that can lead to an unjust arrest for driving under the influence, or DUI.
Oftentimes, the amount of alcohol on your breath is higher than the amount of alcohol in your blood, for various reasons.
One way that your breath alcohol content can get elevated is if more air bubbles move from your stomach to your mouth than normal. This happens whenever you hiccup or vomit, which are, as everyone knows, common occurrences if you've been drinking. Another way for your breath alcohol content to be abnormally high comes from the problem of “residual alcohol” – latent alcohol in your mouth that comes from other sources, like decomposing food.
Together, these two sources of alcohol can skew a breath test's readings, because breath tests aren't able to determine where the alcohol is coming from. To make matters even worse, breath testing machines are often designed to test breath at 93 degrees Fahrenheit. However, exhaled breath is often as hot as 96 degrees Fahrenheit. Because hot air holds more moisture than cold air, and because alcohol is a kind of moisture, this increase in temperature can elevate a breath test reading by as much as 20%.
These inaccuracies can make it possible for you to be arrested and charged for drunk driving, even if your BAC was not at or above 0.08%. Somewhat more shocking, is the fact that breath testing machines, both the portable breathalyzers that police officers carry with them in while on patrol, and the larger, more precise machines that stay at the station, are easily to manipulate. This opens up the possibility for police to actively skew the results of a breath test, if they want to arrest you for one reason or another.
One way for police to manipulate breath testing results is to utilize the fact that breath testing machines don't automatically know what a 0.08% BAC is. They need to be calibrated to know the difference. Of course, it's the police themselves who do this calibration, and if they're in a department that rewards officers based on the number of arrests they make, they have an incentive to miscalibrate the machine to make your actual BAC come back with a higher reading than it should. Even if the police department calibrates it properly, breath testing machines need to be re-calibrated multiple times every year to stay accurate, but this is often overlooked.
Police can also skew a breath test's readings by improperly using it. Many breath testing machines have you blow through a nozzle, capturing your breath in an internal chamber. A display on the outside tells you when this breath chamber is full. If you continue to blow into the nozzle after the chamber is full, alcohol can kick out other air in the chamber, and elevate the reading. Police can use this to make your BAC reading come back higher by simply telling you to ignore the display and to exhale until there's no more air in your lungs instead.
These are situations where having a DUI defense attorney is absolutely crucial. Our past experience defending against DUI charges have allowed us to see all of the ways that breath testing can be skewed or inaccurate. Even the smallest discrepancy can kick a perfectly fine 0.07% up to a 0.08%, and get you in trouble. We know the questions to ask to make sure this doesn't happen to you. Call Lawson and Berry today to discover how we can assist with your case.