If you are unfortunately charged with a drunk driving offense, it is perfectly natural to immediately assume that you have a huge mountain to climb. Most people think that if you are charged with a DUI, there's almost no way to fight it. However, there are plenty of strategies that someone who is charged with DUI can utilize to challenge the crime they are accused of.
There are a variety of situations that could play a role in your DUI offense that may help your case. For example, if you are driving a friend to the hospital due to a medical emergency while you are over the legal limit, the "necessity" defense could be used. Or what if you were forced to drive drunk under the threat of harm or violence? You could use the "duress" defense.
Aside from the specifics of the actual drunk driving stop, there could be procedural problems with your case. For example, your blood or urine sample utilized in the case will have a chain of custody. If that chain of custody is not done properly, then the evidence could be called into question and the case against you could collapse. There are also cases where the police officer in the initial stop may not have even had probable cause to pull the suspect over.
All of this is to say: drunk driving charges are not insurmountable. There are ways in which the accused person can defend his or her case -- or, at the very least, minimize the damage of the charge.
Source: FindLaw, "Defenses to Drunk Driving," Accessed Oct. 1, 2015