[MeanWestTexan]

I thought the blood test could be required only after a traffic accident.

[LongElegantLegs]

Well, from this article, it appears that you only have to be suspected of drunk driving.

[elkfersupper]

I thought the blood test could be required only after a traffic accident.

Blood, breath, or urine is required upon "suspicion".

Otherwise, automatic license suspension for up to a year on the first offense. That way in most States, now.