The drunk driving laws make it a criminal offense to drive a vehicle while under the influence of alcohol (DUI) or while having a blood-alcohol concentration (BAC) of .08% or higher. It is not, however, a criminal offense to be under the influence or to have a BAC of .08% while taking a breath test [...]
Read the complete post at http://www.duiblog.com/2010/06/09/scientific-truth-vs-legal-expediency-presuming-guilt-in-dui-cases/