Prosecutors in Georgia and around the country usually use the results of toxicology tests to establish impairment in drunk driving cases. Police departments use extremely sophisticated and accurate equipment to conduct breath tests, but that does not mean the blood alcohol concentrations they provide are always accurate. If you are accused of driving while under the influence of alcohol, there are several ways that either you or your criminal defense attorney could challenge this kind of evidence.
Maintenance and calibration
Breath testing equipment only produces accurate results when it is regularly maintained and recalibrated. An investigation conducted by reporters from a major national newspaper in 2019 revealed that this important work is often overlooked by law enforcement. The reporters discovered that this negligence often leads to BAC readings that are 40% too high. The investigation also revealed that:
• The software used to operate breath testing equipment is often riddled with bugs.
• Many police departments brew their own chemical solutions to calibrate their machines instead of using proprietary formulas.
• Equipment is sometimes so badly neglected that it becomes a nesting site for rats.
Training, procedure, and the Fourth Amendment
Breath test results may also be excluded and DUI charges dismissed if the police officer involved was not trained how to use the equipment or did not follow established procedures. Even accurate BAC results could be challenged if the breath test was the result of an illegal traffic stop. Officers must have probable cause to pull vehicles over and reasonable suspicion of intoxication to order a breath test, and BAC results may be excluded under the fruit of the poisonous tree doctrine when they do not.
When drunk driving defendants suffer from certain medical conditions, BAC evidence may be of little use to prosecutors even when police officers act properly and the equipment used is in good working order. Conditions like gastroesophageal reflux disease cause vapors to accumulate in the esophagus that can influence breath test results, and diabetics often appear to be far more intoxicated than they actually are because of their higher blood ketone levels increase the amount of acetone in their breath.