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How do dui defense lawyers challenge breathalyzer results?

How do dui defense lawyers challenge breathalyzer results?
Axelrod & Associates, P.A.

How do you challenge breathalyzer results in SC?

You get stopped by a cop for speeding, he says he smells alcohol, and next thing you know you’re in custody at the police station waiting to blow into a breathalyzer machine. You know that you were not under the influence, but will the machine give an accurate result?

Most people who are not cops, prosecutors, judges, or defense lawyers may not know the problems that breathalyzer machines have had across the country – defense attorneys, independent experts, trial courts, and appellate courts for years have pointed out the many ways that these machines give inaccurate results.

But how do you challenge breathalyzer results? If you don’t successfully challenge an inaccurate breathalyzer reading, the prosecutor will use it at trial to put you in jail, take your license, and give you a permanent DUI that cannot be expunged in the state of SC.


First, understand that the breathalyzer machine is not foolproof. It is not a magical black box that always gives the right answer. It is controlled by “secret” software that the manufacturers fight tooth and nail to keep from defense experts, and there are many moving parts any one of which can cause an inaccurate result…

If you don’t know what I’m talking about, read this comprehensive piece of investigative journalism by the NY Times that breaks down the testimony, statements, and appellate opinions by experts and courts across the country showing how the machines are inaccurate because of software flaws, quality control problems, miscalibrations, and design flaws:

But those tests – a bedrock of the criminal justice system – are often unreliable, a New York Times investigation found. The devices, found in virtually every police station in America, generate skewed results with alarming frequency, even though they are marketed as precise to the third decimal place…

The machines are sensitive scientific instruments, and in many cases they haven’t been properly calibrated, yielding results that were at times 40 percent too high. Maintaining machines is up to police departments that sometimes have shoddy standards and lack expertise. In some cities, lab officials have used stale or home-brewed chemical solutions that warped results…

Technical experts have found serious programming mistakes in the machines’ software. States have picked devices that their own experts didn’t trust and have disabled safeguards meant to ensure the tests’ accuracy.

If you’ve been charged with DUI in SC, your goal is probably to get the case dismissed. Faulty breathalyzer tests will not always result in dismissal of the case, although when you challenge breathalyzer results we may be able to get those results excluded from your trial (which can result in dismissal or an offer of a lesser traffic violation).

When Can You Get DUI Charges Dismissed in SC?

Your DUI charges should be dismissed if we can show the court that the officer did not follow the mandatory provisions of SC’s DUI videotape laws. For example, your case may be dismissed:

  • If there is no videotape of the arrest (and no valid excuse for the failure to videotape);
  • If the video does not begin with the activation of the officer’s blue lights;
  • If the video does not show the person’s arrest;
  • If the video does not show the complete field sobriety tests (including the suspect’s feet during the walk and turn and one-legged stand tests);
  • If the video does not show the reading of Miranda rights;
  • If the video does not show the 20-minute observation period in the Datamaster room; or
  • If the video does not show the breath test or refusal.

When the law, policy, or procedure the officer failed to follow is not mandatory (the text says “shall” or “must”), however, the breathalyzer results may still be excluded from your trial…


SLED’s policy and procedures are available on SLED’s website – every SC DUI defense lawyer should be familiar with them and prepared to argue for suppression of breathalyzer results when the arresting officer or Datamaster operator does not follow them.

Your DUI defense lawyer can also access reports on the specific machine, its components, its maintenance records, and your arresting officer through SLED’s database.

Violations of SLED’s policy and procedure during a breathalyzer test that may result in the test’s suppression at your trial may include:

  • Not checking the mouth for foreign substances that can retain alcohol and skew the test result;
  • Use of a simulator solution (the machine tests the simulator solution just before it tests your breath sample – if the solution tests at .08, the machine tells itself it is calibrated) that is out of date;
  • Use of a simulator solution that is the wrong temperature;
  • Not offering a breath test before taking a blood sample for testing;
  • Not completing the breath test within two hours of the arrest;
  • Failure to offer independent tests or affirmative assistance to get an independent test;
  • Not giving both verbal and written implied consent warnings; or
  • Not following any other policy or procedure that affects the reliability of the breathalyzer test.

Can I Challenge the Breathalyzer’s Software?

In several states, DUI defendants have filed motions asking the court to order independent testing of breathalyzer machines or the software that powers them.

Can you do that?

In the right case, with the right resources, a DUI defense attorney can retain experts to evaluate the machine and its software.

You won’t just be fighting the prosecutor and police at that point, however. You will also be fighting the manufacturer of the machine – who will claim “trade secrets” and refuse to provide the software until a court orders it – to have the software tested independently.

In Washington State, for example, a court ordered independent testing of the software. In a report titled “Defective Design = Reasonable Doubt,” the experts found that the breathalyzer is “not a sophisticated scientific measurement instrument” and “does not adhere to even basic standards of measurement.”

So, then the court ordered suppression of all results from that model of machine, right?


The manufacturer then threatened to sue the expert and ordered him to destroy all copies of his report:

After a couple weeks dissecting the Alcotest code, they wrote a nine-page draft report, “Defective Design = Reasonable Doubt.” They planned to dig further, but things went awry when they shared their report with defense lawyers at a convention.

Dräger sent Mr. Walker a letter demanding that he and Mr. Momot ask anyone with a copy of their report to destroy it – including the lawyers who hired them – and to stay silent about the instruments’ inner workings. Facing a giant company, Mr. Walker felt he had no choice but to comply. “I am an ant,” he said.

The expert never testified, and the report was never presented to the court…


Your Myrtle Beach DUI attorney on the Axelrod team will help you to:

  • Investigate your charges;
  • Challenge breathalyzer results;
  • Get your case dismissed if possible;
  • Negotiate a plea to a lesser traffic violation when appropriate; or
  • Take your case to trial with a jury.

Call now at 843-916-9300 or fill out our email contact form to set up a free initial consultation about your case.

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