The 5th Amendment to the U.S. Constitution states that:
"No person...shall be compelled in any criminal case to be a witness against himself..."
By protecting the citizen accused from self-incrimination, the State is put to its required burden of proof - proof beyond a reasonable doubt. In essence, the 5th Amendment is telling the State they cannot rely on forcing a confession out of the citizen accused to meet their burden but that they must, instead, build a case and assemble evidence independent of the citizen's own words.
But you may not have realized that by applying for a Texas driver's license you are, in the eyes of the State, waiving your right against self-incrimination should you be stopped on suspicion of DWI!
The Texas Legislature came up with the notion of implied consent and created a legal fiction that when you applied for your license you knowingly, intentionally and willingly consented to provide a breath or blood specimen upon request. As an additional weapon to subvert your 5th Amendment rights, the State declared that, should you refuse to provide the requested specimen, that we will suspend your driving privileges for at least six (6) months. The State can also tell a jury that they may infer that you had something to hide if you refused to blow into the State's breath machine.
The courts have been all too willing to play along with this charade, fearful of the lobbying power of MADD and victims rights organizations. Now no one is going to stand up and say they support drunk driving - but, once you start to take away the rights of one undesirable group, it makes it easier to take them away from the next group we don't like.
During the 1930's the Nazis played the same game -- they went after the groups the public had no sympathy for... and when no one opposed their repressive measures against those groups, they expanded their program. And, at the end of the day, there was no one left to fight to defend anyone's rights.
I'll leave ya'll with this to chew on: The State cannot compel an accused murderer to provide the evidence that will be used against him, but they can compel a citizen accused of DWI (a misdemeanor) to provide all the evidence the State needs to convict.