A DUI charge requires proof of "driving" beyond a reasonable doubt. The vast majority of cases, the officer pulls the individual over for a moving or fix-it violation and can testify to the actual driving. The reason for the initial contact may be subject to a motion for an illegal stop if there is insufficient evidence to justify the stop and detention of the driver. The driving itself is witnessed by the officer who saw the vehicle move under the control of the person in the driver's seat.
People are arrested for DUI who are not driving or driving is not witnessed by the police. This usually is the case in accident cases where the determination of who was driving is circumstantial if that person is not in the driver's seat when police and emergency personnel arrive. Other ways driving is shown, a person may admit to driving, witnesses may identify the driver, injuries and seat belt bruising may be consistent with driving. DNA can be taken from the airbag, fingerprints may also help I.D. a driver. A person caught in close proximity to vehicle may have keys in their pocket, engine warm, and no one else around. Many times someone claims there was someone else driving, but they don't know their last name, and it is suspicious. People even report their vehicle stolen after they have left the scene, if false, this can result in more serious charges.
In North County, it is not unusual for the Oceanside CHP to contact people pulled over on the shoulder for a "welfare check". This is a legal contact, if the person appears impaired or under the influence, they are usually arrested for DUI. If they have not consumed alcohol since the pull over, then it may be shown that they had to be under the influence at the time of driving to get to that location. If they are asleep in the passenger seat, and no admission of driving and the keys are not in their pocket, it is more defensible.
There can be real issues with proving driving where the officer does not see the driving, especially if there is alternative explanations. This is just one of the areas an experienced DUI attorney can review besides the inital stop, detention, field sobriety tests, chemical testing, absorption rate etc. Nicholas and William Christoph at Christoph Law Offices have been handled over 3000 DUI cases over the last 30+ years across from Vista Courts. Call for a free consultation 760-941-5720.