(1) A blood-alcohol (or breath-alcohol) reading of .08 or higher;
(2) Defendant's normal faculties were impaired.
Obviously, a breath reading is the easiest way to prove DUI, providing the breath machine was working properly and there are no procedural defects that may win the case regardless of the breath test result.
And clearly refusing the breath test still permits prosecutors to proceed on the theory that you were impaired, but just decided not to blow.
But even if you blow and the result is below a .08, prosecutors may still proceed under the same theory as a refusal. The prosecutors will rely on officer testimony and observations to establish that you were impaired, despite the breath reading.
Impairment is a fluid concept. Some people may display signs of impairment after one or two drinks, which may correspond to a breath-alcohol reading of, say, .04.
Impairment can mean defects in motor skills. It can mean blurred vision, slurred speech, and poor balance. Driving is an activity that requires good motor skills. If a police officer believes that you cannot safely operate a car, and suspects that you have been drinking or using drugs, you can still be arrested and charged with DUI even if you blow below a .08.
Now I just mentioned something else. Drugs. Yes, of course you can get a DUI for driving while under the influence of drugs, such as cocaine or marijuana. You can also get a DUI for driving under the influence of prescription drugs, such as oxycodone (OxyContin) or hydrocodone (Vicodin). Even if you have a valid prescription, you can still get a DUI if the medication impairs your driving.
If the police believe that you are on drugs, they may have a DRE (Drug Recognition Expert) assess your appearance and behavior. Sometimes, a DRE can tell (supposedly) that you are high on drugs just by looking at your pupils. Like all expert witnesses, a DRE's credentials are subject to some good cross-examination. If the DRE is 23-years old, has no advanced degrees but took an 8-hour class in drug recognition, of course he or she is going to be a weak expert.
But police sometimes don't look for the truth. They look for what supports their presumption. If they presume you are high, they will look to support it rather than refute it.
Drugs can also be detected through a urine test or a blood test. You may refuse these tests just as you can refuse a breath test. If you have a prior license suspension for refusal, you cannot refuse without being charged with a misdemeanor.
If drugs are detected in your system, it can be argued that the drugs are still there from a previous day's usage. For instance, if you smoke marijuana, scientific evidence shows that the active ingredient, THC, remains in your system for up to 30 days. So if you smoke pot on October 1, 2010, and are pulled over for DUI on October 26, 2010; it is possible that you may still have some THC in your blood.
I practice criminal defense in South Florida. As a DUI attorney, I see all types of cases, from high breath readings to refusals to everything in between.
If you need a DUI attorney, call me today. Remember to retain your DUI attorney within 10 days of arrest so that your DUI administrative hearing can be set. It may save your driving privilege.