Breathalyzer Accuracy and DWI/DUI Conviction Rates

Research indicates that breath tests vary at least 15% from actual blood alcohol concentration. At least 23% (that's about one out of every four) of all individuals tested will have a BAC reading higher than their actual BAC. 1 Therefore, many people convicted of DUI/DWI simply on the basis of a breath test results alone will be innocent drivers who are falsely convicted.

It’s important that drunk drivers, and especially hard core repeat offenders be convicted and/or receive appropriate treatment. But it’s also important that innocent drivers not be falsely convicted of DWI/DUI.

A thoughtful observer has emphasized that

The law presumes every citizen innocent, even when charged with DWI. A judge violates the judicial oath when he or she presumes that a citizen charged with DWI is guilty, gives greater weight to the state's evidence, is predisposed to find for the state, or looks for ways to assist the state in the prosecution of a case. Judges with high conviction rates are NOT fair and impartial but proxies for the prosecution or result-oriented interest groups.

The law imposes the highest burden of proof in criminal matters -- proof beyond a reasonable doubt of every element of the offense. Judges who lower this high burden in DWI cases make it probable that innocent people will be convicted, robbed of their liberty, their property, and their rights. When we permit or encourage judges to lower the burden of proof, we embark upon a slippery slope where expediency and results, rather than justice and law, guide decisions. 2

One judge who has been criticized for allegedly being too “soft“ on defendants is Judge Jerome Leonard of North Carolina, who defends his decisions. “We have taken an oath to uphold the law,“ Judge Leonard explains. “If there’s a reasonable doubt, I have to find that person not guilty.“ 3

The results may not always be pleasing, but the alternative is living in a police state without the protective rule of law.


  • 1. See Breath Analyzer Accuracy.  One veteran of the courts says that the breath tester is “a piece of crap” (Wright, Gary , Alexander, Ames, and Mellnik, Ted. “Judges are not following the law.” Charlotte Observer, August 9, 2004). That seems to be too strong an assertion, but it’s clear that such machines have a substantial error rate.
  • 2. Rawls, Eben. The Intoxilyzer isn’t perfect: Judges in DWI trials must stand for justice despite pressure from public. Charlotte Observer, August 20, 2004.
  • 3. Wright, Gary L and Alexander, Ames. MADD raises heat on Judge Leonard. Charlotte Observer, August 18, 2004.
  • 4. Wright, Gary, Alexander, Ames, and Mellnik, Ted. “Judges are not following the law.” Charlotte Observer, August 9, 20004.
  • 5.Weed, F. J. Grass-roots activism and the drunk driving issue: A survey of MADD chapters. Law and Policy, 1987 (July).

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