Chemical tests are a key factor in every Florida DUI / DWI case. However, while prosecutors rely heavily on chemical test results, they can also help build an effective defense. A blood, breath or urine test that shows that a driver was over the legal limit doesn’t necessarily equal an automatic conviction.  Chemical tests in DUI / DWI cases can be challenged in several ways by an experienced drunk driving defense attorney who is well-versed in the various attacks on breath, blood, and urine testing for alcohol and drugs.

Florida DUI / DWI cases have two separate elements – driving under the influence, and violation of the “per se” laws.  Driving under the influence focuses on whether the driver was impaired by alcohol or drugs to the point that he or she was unable to operate a vehicle with the same caution as a sober person.  The per se element does not center on whether the driver was affected by alcohol or drugs; instead, the focus is on whether the blood or breath alcohol content (BAC) was above the legal limit, now.08 percent in all 50 states. A Florida prosecutor must prove only one element, not both, to obtain a DUI / DWI conviction.

The per se element, or driving over the legal limit, is typically proven with a chemical test of the blood, breath or urine. However, chemical tests are also used to support the element of driving under the influence.  Many forensic alcohol experts believe that every individual is impaired at a certain BAC. Some experts believe that level to be .10 percent, some .08 percent, and the most conservative say that everyone is under the influence at .05 percent BAC. 

Chemical tests are so important to DUI / DWI prosecutions that both the DMV and the courts impose strict sanctions on drivers who refuse to submit to a chemical test after arrest. In Florida, the DMV will suspend a driver’s license for one year on a first refusal and 18 months on a second or subsequent refusal. In court, a driver who refuses a chemical test can be charged with a separate misdemeanor if he or she has refused to submit to a test in a prior drunk driving case.

It’s important to note that while chemical testing may be accurate to determine BAC at the time of testing, it is only an estimate of BAC at the time of driving.  It isn’t against the law to above the legal limit in a police station hours after being behind the wheel; the crime is driving above the legal limit, not having a BAC above the legal limit at a later time.  Because alcohol levels change over time, and continue to rise after a person takes that last drink, this is a critical point to understand.

Chemical tests for drugs can be even more inaccurate than those for alcohol levels.  Drug tests search for metabolites in the blood or urine, not the drug itself.  Also, because of the amount of time that many drugs stay in the system, it is incredibly difficult to demonstrate that a person was impaired at the time of driving.