As a Houston DWI Lawyer I can tell you that “Time of Driving Defense” has nothing to do with whether an individual was drinking at the time they were driving.  It has more to do with how much alcohol was already in a person’s system at the time of driving.

When someone is stopped for a traffic violation, and then ultimately investigated for a DWI, the investigation almost always ends with some sort of test.  These tests are usually either a blood test or a breath test.  These tests are NOT given to the individuals at the scene.  They are typically administered 1-3 hours later at another location.

Sometimes an officer will give a PBT, which is a portable breath test, to an individual to get an idea of how much they have been drinking.  But a PBT is junk science and not admissible in court, so that number is never used as evidence.

As a Houston DWI Lawyer I have seen that what typically happens is the DWI investigation is completed (sobriety tests, questioning, etc), a person is arrested, then they are taken back to the station where the breath or blood test is completed.  It typically takes a minimum of an hour to get to this point (but it can be much longer).  The officers usually have other things to do that take time (paperwork, calling a tow truck, driving to the station, etc).

So, what is the problem with this?  Texas is a Time of Driving State.  This means that it doesn’t matter how much alcohol was in your system at the time you take a breath or blood test, but instead it matters at the time of driving.  And this makes sense, because we should care about the time the person was actually on the road (when people are potentially in danger), not hours later while they are sitting in a room and no one is in danger.  (It is even harder to prove on a Drug DWI).

Let’s take this for example:

Jose is driving and gets pulled over at 1am.  He is arrested, and a breath test is given to him at 2:30am.  His breath test is .085 (which is barely over the legal limit).  For the purpose of this example we will assume the breath test machine is accurate (which many times it is not!).  We don’t care that he was .085 at 2:30am, we need to know what he was at 1am.

Our bodies all work different.  Some of the leading scientists in the world have said that people could continue to be in absorption for a little over 2 hours after their last drink.  And a person can potentially rise .02 an hour.  If Jose had his last drink right before driving, it is possible that at 1am he was actually around a .05 (because he went up .03 in 90 minutes).  .05 IS LEGAL.

This is an elementary explanation, and every case is fact specific, but it gives you an idea as to why the time of driving defense is very important.  Just because you might be over .08 at the time of the test does NOT mean you were over .08 at the time of driving.