Most people know that the legal limit in Texas for intoxication is .08. Even if you don't know what that means, you know that if you take a blood or breath test and the results are over .08 you are going to get charged with DWI. Most people assume that the opposite of that is also true; if the result is under .08, they will let you go. Unfortunately, that's not always the case.
You must be intoxicated when driving - not when you are tested at the jail
How can the police justify an arrest if the breath test result is under .08? The answer is based on several things. First, to be guilty of DWI, you must be intoxicated at the time of driving. It takes time to arrest you, take you to jail, and then give the test. Usually, it's at least one hour, and more likely a couple of hours. Assuming you don't have anything to drink after you're arrested (I think that's a pretty safe assumption), your blood alcohol concentration should start going down at some point. The general rule is that it decreases .01 each hour. (that's an average, which can vary greatly - but that's a topic for a separate discussion). So if your BAC at the jail is .09, and it's been roughly an hour since you were arrested, the police will assume you were .10 when you were driving.
The one time the police will believe you
This is where you can really hurt yourself by answering questions because the police are going to believe you when you tell them when you had your last drink - even though they aren't going to believe you when you say you only had two beers.
So how does this work? Let's say you're stopped at 10 p.m., and you tell the police you had a couple of beers, and the last one was around 8. That means you're blood alcohol concentration should be going down. They take you to the jail, and you agree to take the breath test, believing you are going to pass. The test is administered at midnight, and you blow .07. When they tell you the result you feel pretty good until they tell you that you are being arrested anyway. The rationale is that your blood alcohol should have gone down by .02. so you were actually .09 at the time of driving.
Remember telling them you only had two beers. If they believed you on that, they wouldn't even give you a test, because your test results would be under .01 - since your body would have eliminated the alcohol by the time you took the test. What it comes down to is that they believe you when you had your last drink - even though they know you probably aren't being truthful, because you probably finished your last drink right before you left the bar. But they don't believe you only had two drinks.
That's only one scenario. The definition of intoxication is having a blood alcohol concentration over .08, or not having the normal use of your mental and physical faculties. So even without the test results, they could argue the field sobriety tests show you were intoxicated.
Mind-blowing isn't it?
This is one situation where you definitely need to find an experienced lawyer, who understands the concepts of "retrograde extrapolation", and how to point out the limitations in the state's theory. You also need a lawyer who understands the field sobriety tests, and is able to attack those.
If you've been arrested for DWI, and want to talk with us about your case, please give us a call at (254)-296-0020, or use the contact form on this page.