When the prosecutors are trying to convict someone of a Driving Under The Influence Charge, they must prove two separate elements beyond a reasonable doubt. 1) That the person was under the influence and 2) that the person was driving.
It may often be straightforward to prove that a person is intoxicated, especially when they have submitted to a blood alcohol test and the date results demonstrate a BAC present in their blood stream. Driving on the other hand, may not be as easy to prove in all cases.
Lets consider two different examples, one in which driving is straightforward, and another in which it is not.
David has had a few drinks and is driving himself home. While he is on the freeway he is speeding, hoping to get home faster. He is stopped by an officer and is asked to pull over. After procedural tests are given, he is arrested and taken into custody under suspicion of driving under the influence.
There is not too much room for argument in David's case. He was driving the car when he was pulled over by officers. They will easily meet the burden of proving this element.
In comparison, Danny goes to a bar with his friends. When he leaves the bar, he realizes he is under the influence and decides that it is not a good idea for him to drive him. So he gets into his backseat, uses a blanket he has left in the car and falls asleep. The car remains in the parking lot, and the keys are in Danny's pocket, while he lays in the backseat. Danny has receipts from the drinks he bought at the bar in his pocket. Officers notice the car and question Danny as to driving under the influence.
Prosecutors are not going to have an easy time proving that Danny was driving. Not only were his keys not in the ignition, he was blatantly asleep in the backseat with a blanket and not in the driver's seat, he was still parked at the same bar at which he has receipts to prove he was at. There is a strong argument to be made that Danny was not driving and made a decision to not go anywhere.
If driving is an issue in your case and seems that the facts could demonstrate that you were not driving, Prosecutors would not be able to meet all elements required for a DUI conviction. If prosecutors have a hard time proving all elements, or fail to do so, your case must be dismissed. If they refuse to dismiss, it would be a good idea to take it to Trial and put the matter before a Jury. Consult with an experienced San Diego DUI Lawyer who can analyze the specific facts of your case and make a determination of whether you have good chances to get your case dismissed.