Yes, it is possible for someone to be prosecuted if their BAC is under .08.  In CA, there is a zero tolerance rule if you are under 21, since by law, you are not supposed to be drinking. A person under 21 will be prosecuted for underage drinking with even a .01 (i.e. the .08 does not apply).  In an under 21 case, the drivers license is suspended for a year.  Also, you must request a hearing at the DMV within 10 days of your arrest or you lose substantial rights.  Additionally, even if you are over 21, you could potentially be charged with a DUI even though you were under a .08 as per Vehicle Code section 23152(a) (in other words, you can be charged regardless of your BAC if you are objectively impaired).At this point, you should consult with an experienced DUI attorney in the area of where you were charged.  Skilled legal counsel may be able to get the charges dismissed/reduced, or win at trial.