DWI and the "While Defense"

DWI lawyers know that most times their defense will be “the State can’t prove my client was intoxicated”. This usually comes up in breath or blood test refusal cases, where the defendant does well enough (not perfectly, just well enough) on the field sobriety tests.
Sometimes, the defense is that the State can’t prove that my client drove or operated a motor vehicle. This might involve the police arriving on scene after a collision, or after the driver is pulled over on the side of the road.
But the least common DWI defense is what I call the “while defense”. Yes, the state can prove my client was legally intoxicated (at some point). And yes, they can prove he was operating a motor vehicle. But they can’t put both of them together at the same time, and therefore, he wasn’t Driving While Intoxicated.
This defense is realistically possible when the defendant provides a breath or blood specimen where the analysis shows that the alcohol concentration is over .08, but is for example, under .10.
Of course, the defendant didn’t actually provide that specimen while driving, but instead, some time after the fact. I’d estimate that in most Austin DWI cases, my client’s breath or blood sample is taken somewhere between 30 minutes to 2 hours after the arrest.
Why so long?
Well, there’s sometimes a delay while the original stopping officer waits for an Austin Police Department DWI task force officer to arrive on the scene. That officer then conducts an interview, and administers field sobriety tests. The officer might conduct an inventory of the vehicle, and will certainly read the DIC Statutory Warning to the defendant, asking for a specimen of breath.
Then there’s the trip to the police station, where there may be an additional wait. (The recent addition of the BAT-Mobile, or Breath Alcohol Testing Mobile Unit has cut down that wait – but that’s fodder for another post.) And depending on where in Austin the client was stopped, the trip to the station or the DWI mobile unit can take quite some time as well.
The point is that having a BAC of .085, for example, 30 to 45 minutes after the driving, does not in and of itself prove that the defendant was driving while intoxicated. Depending on various factors, primarily the particular drinking pattern that night and the stomach contents, it is possible for the Defendant’s BAC to be higher at the time of the test, than it is at the time of driving. It is also effected by variations in human physiology as well.
This is most likely in scenarios where the defendant’s last drink was very near the time of driving; which given what happens at closing time, is not an unlikely scenario at all.
This isn’t just some crazy DWI defense lawyer theory here either – it’s both basic common sense, and basic science. So basic, that even the CMI manual for the Intoxilyzer 500 (used for breath tests here in Austin) admits that the defendant’s actual breath alcohol content at the time of the test may be “higher than, lower than or the same as” the BAC at time of driving.
[Last Note: in explaining this over the years, I really have come to label this the “while defense”, because it seems to make sense when I explain it in this context. I should note, however, that the more formal term for it is the “rising BAC defense”, meaning that if the defendant’s BAC was still rising at the time the vehicle was pulled over, then it’s likely that it was below the test measurement at the time of driving.]