Research found that statistics taken around DUI, OUI, DWI, and the like, varied greatly if they could be found at all. Most rates were based on convictions.
The first step in seeking a defense to get the charges dropped or the case dismissed is … call a DUI lawyer. This is your first line of defense. At least consult with an attorney. An initial consultation is usually free.
Statistics in California for the period between 1997 and 2006 was between 75 percent and 85 percent conviction rate. In 2006 in California, 90 percent of DUI arrests ended up with convictions. Another site offered up a PDF that cited statistics from various counties across the US. Some conviction rates were as low as 63 percent while several were 85 to 95 percent. Actual dismissals of charges occurred at rates, when stated, of around 1.5 percent. One country cited about a 10 percent dismissal rate. Rhode Island cites a rate of about 67 percent convictions. From 2000 through 2011 Connecticut cited a 50 percent climbing to a 70 percent dismissal rate, but only from allowing 1st time offenders to take a course whose completion got the charges dismissed. Washington State cites an average of 32 percent dismissal.
The reasons for dismissal are many, but a few stand out. One of the biggest reasons that a dismissal occurs is the reason that the police officer had for stopping you in the first place. This is known as “probable cause”. Every state in our Union requires that a police officer must have a very solid reason for a traffic stop, unless it is a legal roadblock where every car is stopped. In court at the DUI hearing, the police officer must testify, if asked, what the reason was for the original stop. The reasons for stopping a vehicle are also many, and not necessarily directly tied to drinking. If someone in the car discards trash onto the road while observed by a police officer, the officer can stop the car for that reason, then, smelling a distinct odor of alcohol, had probable cause for DWI or DUI. The rest is the tests and possible arrest. (nice rhyme, yes?) Another typical reason is if the police officer does not appear for the hearing, there is a possibility for immediate dismissal, or another hearing date. Most states have a time limit between the arrest and the hearing. If that time limit is exceeded, especially with an extension, the case could be and should be dismissed.
At your arrest, were you read your Miranda rights? If not, the case must be dismissed. Some sites and contributors recommend attacking the veracity of the field sobriety tests and the Breathalyzer. Some cited the loss of a blood test results.
The following site has a couple of examples of hearing cases where the burden of proof that a crime of DUI had been committed was found to be insufficient. This led to dismissal of the charges.