If drugs were present in your car or on your person during your arrest, they may have a bearing on your DUI. However, if your DUI is based only on alcohol consumption and law enforcement does not have any evidence that you are under the influence of the drugs found, it may be possible to sever the charges so that the presence of controlled substance is not used against you in your DUI prosecution. Commonly marijuana is found in the car or on the person of an arrested driver, but is not in the system of or was not thought to be influencing the driver at the time of the driving incident. If this is the case your defense attorney can and should file the appropriate motion to prevent the state from using this evidence against you in the DUI prosecution. This does not mean that the drug case will go away, but it may need to be brought in a separate case or be tried separately from the DUI.