DUI Breathalyzer Accuracy

In many DUI cases, breath analysis is used as a method to test for blood alcohol concentrations. Scientists have conducted studies regarding breath alcohol analysis and most have agreed with Dr. Michael Hiastala, Professor of Physiology, Biophysics and Medicine at the University of Washington, in concluding that breathalyzer accuracy is inherently unreliable:

“Breath testing, as currently used, is a very inaccurate method for measuring BAC. Even if the breath testing instrument is working perfectly, physiological variables prevent any reasonable accuracy.  Breath testing for alcohol using a single test method should not be used for scientific, medical or legal purposes where accuracy is important.” [Hiastala, Physiological Errors Associated with Alcohol Breath Testing, 9(6) The Champion 19 (1985).]

Safeguards for Breath Testing

It is estimated that courts have reserved DUI convictions because breathalyzers accuracy unreliable. There are four “safeguards” for breath testing according to Dr. Kurt Dubowski, a longtime advocate to strict procedures for reducing the many sources of error in DUI breath testing. [K. Dubowski, The Technology of Breath-Alcohol Analysis (NIAAA 1991):

  1. A pre-test deprivation-observation period of at least 15 minutes.
  2. Blank tests immediately preceding each breath specimen collection step.
  3. Analysis of at least two separate consecutive breath specimens, taken two to ten minutes apart (different results from duplicate analysis may indicate such problems as radio frequency interference).
  4. An appropriate control test accompanying every subject test.

The National Safety Council Committee on Alcohol and Drugs has recommended at least two separate breath samples should be collected and analyzed individually. Tests should be collected at intervals of more than two minutes and less than ten minutes. All results should be obtained and reported.

Breath Analyzing Machines

The most economical method in any DUI investigation is breath analyzing. There are number of different breath analyzing machines in use today:
  • Intoxilyzer 5000
  • Intoxilyzer 9000
  • BAC DataMaster
  • Intoximeter EC/IR
  • Draeger AlcoTest 7110
  • Portable Draeger AlcoTest 7410.

These machines use their own mechanism for analyzing the alcohol content called infrared spectroscopic analysis. This is the principle that alcohol vapor captured in a chamber will absorb light waves of a certain frequency when beamed through it. The Breathalyzer uses a different technique called the “wet chemical” technique.

California DUI defense attorneys should be aware there are a various of problems in approaching a DUI case involving a breath analysis. For a review of many of these problems, see Taylor & Taylor’s presentations “Breathalyzer and Breath Test Analysis” and “Breathalyzer Accuracy."

Back to Top