About twenty years ago, Texas lawmakers approved a per se DWI law. Before the legal change, a BAC level above the legal limit was a presumption of intoxication. Now, people with a BAC over the limit may be intoxicated as a matter of law. Not surprisingly, the DWI conviction rate increased significantly.
In the early and mid-1990s, peace officers substantially increased the number of drunk driving arrests. Today, there are over 1.4 million DWI arrests every year. That's almost 1 percent of the licensed drivers in the United States. In certain situations, peace officers are even more aggressive than normal in this area.
Until recently, the DWI eye test, which is also known as the Horizontal Gaze Nystagmus (HGN) test, was considered the most reliable of the three tests in the National Highway Traffic Safety Administration three-test battery. Now, it is considered the least reliable one.
Roughly four out of five DWIs involve breath or blood tests (mostly breath tests). The conviction rate in breath test cases is over 80 percent in most jurisdictions, and in some places, it is closer to 90 percent.
Largely since Texas does not have a refusal-to-submit law, about one in five DWI cases are chemical test refusal cases. Refusal-to-submit laws, like the one in Florida, make breath test refusal a separate criminal offense.
In many places, "drugged" driver cause more fatal crashes than "drunk" drivers. So, Tarrant County prosecutors pursue these cases very aggressively. Prescription drugs and marijuana account for a little over half of drugged driving prosecutions in Texas.