A South Carolina judge has given people hoping to beat DUI charges some new ammunition.

A breath test is not valid if the officer tells the person taking it to blow harder, Columbia Municipal Judge J. Steedley Bogan ruled last week.

An officer told a woman suspected of drunk driving to blow harder into the mouthpiece of the Datamaster breath analyzer several times during a two-minute test, according to testimony upon which all sides agreed. Breath tests are videotaped under S.C. law.

The machine’s manual and an instruction video on its operation warn officers not to tell people to blow hard during the test, the ruling noted.

Blowing hard can mess up the test, because the machine is calibrated for an even flow, attorney Joe McCulloch argued.

He brought in a chemist who has studied the machines to back him up.

The S.C. Criminal Justice Academy trains officers to use the machines.

Lt. Dale Smith, traffic safety program manager for the academy, said he did not think an order to “blow hard” would skew the results, according to The State newspaper.

The judge ruled that telling a person to blow hard violates proper procedure when administering the test.

“There is simply no way to avoid the unavoidable conclusion that instructing a subject to ‘blow hard’ is not a proper procedure,” Bogan said in his ruling.

The ruling means that the breath test can’t be used as evidence when the case goes to trial.

McCullough said the ruling could affect DUI cases across the state.

“I hope this ruling broadcasts to the law-enforcement community that this is not a proper practice,” he said. “It could very well affect hundreds of cases in which this improper procedure has been used.”

McCulloch said he didn’t believe officers were telling people to blow hard deliberately to inflate the test results, but because the machines are hard to use.

Spokespersons for Columbia’s legal department and police department could not say if any new instructions were issued to officers after the ruling.

The State Law Enforcement Division oversees the machines but not the training on how to use them, SLED spokesman Thom Berry said.

Charleston DUI attorney Timothy Kulp said he believes the ruling is a significant victory for those worried about the accuracy of the breath machines.

“These machines are very complex,” he said. “When proper procedures aren’t used, problems are going to arise.”

Reach Dave Munday at 937-5553 or twitter.com/dmunday.