Driving While Intoxicated in Texas (or DWI) is probably one of, if not the most arrested offenses in the State. In order for the police officer to make an arrest, the cop only has to have probable cause in order to take you to jail. In other words, the cop has to be able to testify that he probably believed that you had lost the normal use of your mental or physical faculties (i.e. that you were intoxicated).
The District Attorneys office has a much more difficult task at trial. The prosecutor must prove that the citizen accused was intoxicated beyond a reasonable doubt...which is the highest burden of proof in our American system of jurisprudence.
If there is aninjury to another person in an accident involving an intoxicated driver, then the penalty range can be enhanced to a felony.