On top of all the confusing things that will be thrown at you when you are charged with a DUI, add BAC (or blood alcohol content) to your list. By the way, this can also be referred to as blood alcohol concentration just to confuse you a little more!
Your BAC is the amount of alcohol found in your blood steam. This can be measured in two ways: percentage by mass or mass per volume. For example, if you had a BAC of .02%, this means that there is 1 gram of alcohol for every 500 grams of your blood.
In order to determine your BAC, a blood sample must be taken. A qualified medical professional must be the one administering the test. It must also be taken, analyzed and transported in the appropriate manner. If any of these things are done incorrectly, your lawyer can rule your blood test to be inadmissible as evidence against you.
BAC is utilized by law enforcement as a way of setting a legal limit and to define intoxication. Currently, every state has adopted a legal limit of 0.08 as the allowed level of intoxication while driving.
In some states, you can be arrested for driving with a BAC of less than 0.08. And many states have zero tolerance laws aimed at underage drivers. Zero tolerance laws make it illegal for a person under age 21 to consume alcohol. The punishments for this are also severe.
Blood alcohol tests have taken on assumptions about the individuals being tested because alcohol affects everyone differently. A critical assumption is the ratio of one’s breath alcohol content to their blood alcohol content (known as the partition ratio). This ratio is an average at 2100:1, but the actual ratio for an individual can vary from 1300:1 to 3100:1.
And these ratios can have a dramatic influence on the accuracy of field sobriety tests and a person’s actual level of intoxication. Let’s say for example your actual blood alcohol content was .08 and your partition ratio was 1700:1. That would mean that your breath alcohol content would be higher at 1.0 on the breath test!