Drivers arrested for DUI / DWI in Florida must submit to a chemical test of their blood, breath, or urine to determine blood alcohol content (BAC). Urine tests are considered the least reliable form of chemical test. However, because urine tests are inherently error-prone, the results can be effectively challenged in court. A Florida attorney who focuses on drunk driving cases will aggressively question the results of a urine test as part of a winning defense strategy.

Certain protocol should be observed when police administer a urine test in a DUI / DWI case. The driver should be given a certain amount of privacy while still ensuring the accuracy of the sample. Drivers should be advised to empty their bladders, wait 20 minutes, and then go again.

Errors in urine testing are quite common. Police and technicians often fail to follow the proper procedures. And because the test involves water instead of blood, BAC results in urine tests are usually inflated. The concentration of alcohol in urine is approximately 1.33 times the concentration of alcohol in blood. 

Urine tests are equally unreliable in cases where the motorist is suspected of driving under the influence of drugs (DUID), because it’s impossible to determine when a drug was used.  Urine tests detect only metabolites – inactive traces of previously ingested substances – not the drugs themselves. For example, a person who smoked marijuana on a Tuesday night may test positive on Friday, long after the effect of the drug has worn off.

Problems with urine testing for alcohol and drug use have been widely documented. A survey conducted by the National Institute of Drug Abuse found that 20 percent of labs studied had erroneously reported the presence of illegal drugs in drug-free urine samples. Drug screens of urine also tend to confuse similar chemical compounds – legal, over-the-counter medications have been mistaken for illegal drugs.