Most DUI case are proved with a breath test or a blood test. The federal government has set limits on what blood concentrations are legal to drive. And those legal limits have been being reduced year after year since the 1960's. From .15 to .10, and then from .10 to .08. Now there are efforts afoot to reduce the legal limit to .05. This is a level at which there is literally no measurable impairment from alcohol.
There are many problems with breath testing. It is inexact. It doesn't actually reflect blood alcohol levels, at least for the first few hours after drinking). It measures "deep lung air," which is uniquely rich in alcohol, despite statutes which merely say that the test should measure "breath."
Here are some of our articles about breath and blood testing:
- The 3-2 Rule-Two Simple Steps to blowing lower on the breath machine
- Is a blood test automatically done when there is no breath test?
- The Seven Secrets of the Intoxilyzer-What the police don't want you to know.