How does the state determine the blood-alcohol level of a person? Are they not causing the person to unconstitutionally be a witness against himself if they extract blood or breath?
The 5th Amendment to the Constitution.
No person shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a Grand Jury, except in cases arising in the land or naval forces, or in the Militia, when in actual service in time of War or public danger; nor shall any person be subject for the same offense to be twice put in jeopardy of life or limb; nor shall be compelled in any criminal case to be a witness against himself, nor be deprived of life, liberty, or property, without due process of law; nor shall private property be taken for public use, without just compensation.
Yeah, I don't know exactly, but I know that it has already been litigated numerous times, in favor of the state.