D.C.’s Continuing Problems With The Accuracy of Breath Test Machines in DWI Cases

by Jamison Koehler on November 23, 2010

Last spring, after it was revealed that two years’ worth of breath test results in D.C. were suspect, the Office of the Attorney General (OAG) sent out a letter to defense counsel assuring them that the calibration problems had been resolved.  What the OAG’s office did not say was that, although the calibration problems may have been worked out, all three police departments in D.C. were continuing to experience problems with the accuracy of the breath test machines.

Many criminal defense lawyers think this was a deliberate misrepresentation.  Others assume that whoever wrote the letter just didn’t understand the difference between calibrating a breath test machine and ensuring its accuracy.

Bryan Brown, a prominent DWI attorney in DC, has described the difference as follows.  If you put a 50 pound weight on a scale and then set the scale to show that the weight equals 100 pounds, you have successfully calibrated that machine.  You can now put another 50 pound weight on the scale and it too will be measured at 100 pounds.  The scale is measuring exactly as you have instructed it to.  But the results are completely inaccurate.

This is what has happened in D.C., and the problem only gets worse.  According to Brown, the police have used their own solution to calibrate the breath test machines.  They have then used this same solution to confirm the accuracy of the machines. What’s more, the police have failed to use the required three points of measurement.  As Brown puts it, a scale can be completely accurate in measuring at 100 pounds but still be inaccurate at 50 pounds or 150 pounds.  You need to gauge the accuracy of the scale at these weights as well.

While the precise scope of the problem in D.C. is still being determined, Brown believes that breath test problems go far beyond the two years’ worth of suspect tests acknowledged by the OAG, that the problems extend beyond the Metropolitan Police Department to the Capitol Police and Park Police departments, and that the machines have been deliberately calibrated to show test results 20 to 40% higher than they should.

The implications of this are astounding:  It means that thousands of people have been wrongly convicted of driving while intoxicated.  Thousands of people have had their licenses suspended or revoked; their criminal records besmirched by a wrongful conviction.  Many of these people have served jail time.

For the time being, the OAG has not been introducing breath test results in drinking-and-driving cases in D.C.  The prosecutions have proceeded instead on the driving under the influence (DUI) and operating while impaired (OWI) charges alone, offenses which do not require proof of any specific blood alcohol levels.

Clearly, however, the problems experienced in D.C. and the OAG’s reaction to the problems have severely undermined any confidence the public may have had in the fairness of drinking-and-driving prosecutions.  They will also influence the number of people who refuse to take a breath test and affect how these refusals are treated by the courts.  Stay tuned.

2 Comments on “D.C.’s Continuing Problems With The Accuracy of Breath Test Machines in DWI Cases

  1. From an engineering view, I’d put it in terms of precision and accuracy. Accuracy is how close the measurement is to the true number. Precision is getting the same measured value repeatedly, even if it is inaccurate. Colloquially, precision and accuracy are used synonymously, but in the scientific method the distinction is important.

    I’d think the calibration process would be used to check or adjust the accuracy of the machines, but I am not familiar with the devices. So, to have resolved calibration issues but have the machines remain inaccurate makes no sense to me.

    These issues pop up every so often. It seems there may be a need for a uniform standard — from government or industry — for the manufacture, operation, and calibration of these machines, if there are no such standards already.

  2. Mr. Crowley:

    The distinction you make in your comment is the very type of thing my father, a former English professor, would have enjoyed thinking about for hours. And pre-med and engineering students in college often complain that they need to take English courses.

    I recognize you from Twitter. Thanks for commenting.

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