The law in Texas does not say that it’s legal to drive with a breath or blood alcohol concentration of under .08.
There are two alternate definitions of intoxication in Texas when it comes to DWI. The first, everyone is somewhat familiar with: the .08 BAC per se limit.
The second however, is the alternate definition of intoxication: not having the normal use of your mental and/or physical faculties due to the introduction of alcohol, a controlled substance, a drug, a dangerous drug, a combination of two or more of those substances, or any other substance into the body.
The second definition is what the State uses as their theory every time they prosecute someone in Texas without a breath, blood or urine sample. Or, when the person provides a specimen and it’s under .08.
The law does not say that it is legal to drive if your BAC is under .08; it only gives the State more ways to attempt to prove your guilt if you provide a sample over .08.
Think of it this way: A sixteen year old, weighing about 120 pounds, drinks 2 beers, never having consumed alcohol before. Depending on several factors (size of beer, alcohol content of beer, stomach contents, etc.) it’s very likely that our hypothetical teenager is not over “the legal limit” of .08.
However, since this is his (or her) first time having a beer, he (or she) may indeed be impaired, which is essentially the alternate definition of intoxication for DWI.