California has funny rules about traffic citations - if the police can't positively identify you as the driver of the car when the infraction occurred, they can't cite you. Even if the car wasn't stolen and you're the only one with a set of keys. It could have been anyone driving. And if they can't establish that you were actually drunk at the scene, they can't charge you with DUI. You might have got drunk afterward.
But as a police officer, being charged with a DUI could get you booted from the force.
For these reasons, there is a shameful number of hit-and-runs committed by police officers in California. Just a couple years ago there were four officers in Manhattan Beach (a very small department) suspended for plowing into a parked car while cruising around drunk - and a fifth officer suspended for covering it up (he was first on the scene, and let them walk).