Unlike many other states, where driving while impaired and having a blood alcohol content (BAC) of .08 percent or greater are two separate crimes, Florida views these actions as a single offense – DUI / DWI or driving under the influence. A prosecutor needs to prove just one of the two elements in order to convict a motorist of drunk driving.

The allegation that a driver had a BAC of .08 percent or greater – often referred to as the “per se” charge – is fairly straightforward. The prosecutor will introduce the driver’s chemical test results based upon a blood, breath, or urine sample as evidence that the motorist’s BAC exceeded the legal limit. However, even though police and prosecutors like to believe that this evidence is ironclad, it can be successfully challenged in court.

The second allegation of driving while impaired is more complex, and is typically proven with circumstantial evidence such as the driver’s field sobriety test results. Being under the influence is typically defined as a driver whose physical or mental abilities are impaired to such a degree that he or she no longer has the ability to drive a vehicle with the caution characteristic of a sober person under the same or similar circumstances. Evidence of a driver’s impairment also can be effectively challenged.

To understand how defense attorneys successfully protect their clients in the face of such evidence, it’s useful to remember how our criminal justice system works. Prosecutors in criminal cases have the burden of proving their cases beyond a reasonable doubt.  If the prosecutor’s case is not 100 percent free of reasonable doubt, the accused motorist is entitled to a judgment of not guilty.  This standard, the requirement of proof beyond a reasonable doubt, is fundamental to our criminal justice system.

Skilled criminal defense attorneys use this standard to their best advantage. An attorney needs to convince just one juror of reasonable doubt about one element of the offense, and the case is won. If one juror refuses to vote for a guilty verdict, the trial ends in a hung jury, and the prosecutor often opts not to retry the case.

The allegation that the driver’s BAC exceeded the legal limit of .08 percent – now the legal limit in all 50 states – can be defended by attacking evidence such as the driver’s chemical test results.  Chemical analysis of a driver’s blood, breath or urine to determine alcohol levels is far from foolproof. A skilled attorney will have any samples independently tested to determine whether errors were made in collection or analysis, or whether the result reflected an inflated BAC.

Similarly, circumstantial evidence of impairment also can be effectively challenged. Field sobriety tests, which are purported to assess physical and mental impairment from alcohol intoxication, are highly subjective, and the results can be interpreted in a number of ways. Other observations made by the arresting officer can also be questioned during an effective cross-examination.