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Florida DUI Defense Attorney > Blog > DUI Defense > How Do DUI Blood Tests Work?

How Do DUI Blood Tests Work?


Police have several ways to determine whether or not a driver is drunk at the time of an arrest. The most popular is field sobriety tests, but they are also the least accurate. Breathalyzer tests are more accurate but do have a margin of error. The most accurate way to determine if someone is intoxicated at the time of an arrest is by using a blood test.

Blood tests for alcohol work under the assumption that alcohol enters your bloodstream. The amount of alcohol in your blood can be tested by heating up a blood sample. The amount of alcohol that evaporates when the blood test is conducted can be used to measure the defendant’s blood alcohol content (BAC).

Blood tests can also be useful for measuring drug content in a defendant’s blood stream. They can be used to test for drugs like cocaine and heroin alongside other intoxicants like computer duster. The blood test tests for drug metabolites in the blood.

Only certain individuals are qualified to administer blood tests 

Blood tests, unlike other forms of chemical testing, require that only certified individuals administer the tests. For this reason, they cannot be administered on the road or while an arrest is taking place. They can only be administered at a police station or in a hospital by a certified phlebotomist. In cases where a non-certified individual administers the blood test, the defendant can challenge the blood test in court. The court may be unwilling to accept a blood test that was administered by a non-certified individual.

Blood tests for DUI are more complicated to perform than breathalyzer tests. With a breathalyzer test, the machine returns a reading for the officer based on breath alcohol content that is translated into blood alcohol content. With a blood test, the sample must be stored and refrigerated. If it is not refrigerated, the alcohol content can ferment the blood causing it to give a higher reading than the defendant’s actual BAC.

Do I have to consent to a blood test? 

In 2016, the United States Supreme Court ruled that law enforcement must get a warrant to compel an individual to give blood for the purpose of determining whether or not they are under the influence. This means that blood tests are usually only performed in scenarios where there is a fatality. In most other cases, breath tests will become the evidence used against you in court. In the event that there is a fatality, however, the court can issue a warrant to obtain an individual’s blood for the purpose of testing.

In hospital settings, they often draw blood for the purpose of testing. The Supreme Court also ruled that no warrant is necessary to draw blood when the individual is unconscious. The blood tests can be used against the defendant if they are taken to the hospital unconscious. The majority of these tests are administered in hospital settings.

Talk to an Orlando DUI Lawyer Today 

FL DUI Group represents the interests of those charged with DUI in or around Orlando, FL. Call our Florida DUI defense lawyers today to schedule an appointment and we can begin discussing your defense strategy immediately.

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