Many people in Scottsdale, Arizona may not think about this when they read a story about someone who gets arrested on the suspicion of driving while under the influence of alcohol, but the breath test used during that stop may have been faulty or improperly used. It's easy to just assume "that guy is guilty," and, as such, the equipment or the processes used by the police were correct and appropriately handled. To the contrary, there are plenty of cases where a DUI arrest was mishandled, leading to dropped charges against the accused person.
The reliability of breath test and other alcohol-measuring equipment has come under fire in recent years. Some breath tests have proven to be inaccurate; while some police officers do not follow the instructions for the appropriate use of a breath test. In that scenario, any evidence garnered from the test comes into question.
For example, consider the situation facing thousands of people in Massachusetts right now. These people have been arrested on the suspicion of DUI, and they are facing serious consequences. Just one thing: the breath tests that were used on them did not have an instruction manual, so there is no way of knowing if any of the police officers followed the rules and laws that govern such breath test equipment. As a result, criminal defense lawyers are asking for all the cases to be reviewed, and potentially dropped.
Anyone accused of a DUI has rights, such as the right to due process. If the police botch a DUI investigation, the person accused of the crime could be let off with reduced penalties or no penalties at all because they police did not follow due process.
Source: Sentinel and Enterprise, "Lawyer: Breath test fails legal sniff test," Michael Hartwell, Oct. 6, 2013