DUI breath tests no good when South Carolina cops give bad instructions

In many drunk driving cases, breath tests results are one of the foundational pieces of evidence relied upon by the prosecution. Yet, just like any other test, the results can be skewed when a breath test is not properly administered.

"Blow hard" not correct instruction, thus breath test evidence was thrown out

In an order issued in mid March, a judge in Columbia, South Carolina threw out breath test results that prosecutors sought to use against a suspect in a DUI case.

After being pulled over, the suspect was asked to submit to a breath test for alcohol. During the two-minute sampling period, the arresting officer instructed the suspect several times to "blow hard" into the Datamaster breathalyzer machine being used to administer the test.

However, at a hearing before the judge, a Datamaster instructional video was shown that specifically advises officers against ordering someone to "blow hard." An expert witness also testified that Datamaster results can be affected by altering the breathing pattern, that the best alcohol breath test results come from a strong, continuous exhalation and that some commentators believe blowing harder causes higher results.

The judge ultimately concluded that there was no way around it: instructing a suspect to "blow hard" into a Datamaster machine was not proper procedure. Thus, he issued an order prohibiting the prosecution from using the breath test results as evidence when the DUI case goes to trial.

Many types of procedural deficiencies can call DUI evidence into question

This case was before a municipal judge, and a city judge's opinion is not binding on other jurisdictions. Just the same, the case raises important questions of police procedure and gives a prime example of one way your DUI defense attorney may challenge the evidence against you in a drunk driving case.

Proper police procedure is essential; if corners are cut, the reliability of evidence is called into question. When your attorney can show that police have collected evidence in violation of the proper procedures, you may be able to get this evidence thrown out and therefore undermine the case against you.

The example outlined above, an officer incorrectly instructing a suspect to "blow hard," is an instance of not following training. When the personnel administering a test are not qualified - for instance, they are not licensed to conduct the test or are not doing the test properly - test results may be challenged. This is not just limited to officers conducting roadside breath tests; someone taking a blood draw or urine sample to perform alcohol tests must also be qualified.

Maintenance is another aspect of proper procedure. Breathalyzer machines do not deliver consistent, accurate results when they are not correctly calibrated. Even if a police officer administered an otherwise textbook breath test, showing that the department did not conduct routine maintenance on its breathalyzer machines could impair the authority of test results.

Chain of custody issues are one more potential procedural weakness in a DUI case against you. Evidence from a crime must be treated delicately; it is important to track who has control of the evidence and when in order to ensure that evidence is not tampered with. Chain of custody problems can arise when there is a gap - for instance, a lab tech forgot to document his or her receipt of a blood sample - or when there is reason to believe that someone in the chain of custody is not trustworthy.

Talk to a South Carolina drunk driving attorney about your case

Procedural deficiencies are just one aspect of a drunk driving case that an experienced South Carolina DUI defense attorney may be able to turn to your advantage. If you've been accused of drunk driving, talk to a defense attorney today to begin building your defense.