The short answer is yes, you can be convicted of a DUI with a test result under the legal limit of 0.08.  The prosecutor can proceed on the theory that you were "driving a vehicle under the influence to a degree that rendered you incapable of safely operating" a motor vehicle.  In other words, you were impaired to the extend you were not safe to drive despite your breath alcohol level falling under the legal limit.  You would normally see this charged when there is a crash involved or the driving behavior was very erratic and placed others in harms way.  But what about a standard traffic violation, like speeding? can that serve as "unsafe operation" while under the influence? The answer is yes, it certainly could if the arresting officer testifies your performance on the field sobriety tests (walk and turn; one-leg stand; HGN, counting, etc.) indicated signs of impairment.

You can not assume you are immune from prosecution if your test result is under 0.08.  Prosecutors can proceed on DUI case with or without a test result. For instance, on a test refusal case, the prosecutor relies solely on the driving behavior and the field tests to persuade the Judge or jury for a conviction of the defendant.  A low breath test does make it harder for the prosecutor to convince a judge or jury of the driver's guilt.  But it must be considered when weighing the options between a trial and applying for diversion.  A conviction for DUI will trigger a 30 day suspension of your license followed by 6-months of the interlock. 

It is best to consider the Judge who will decide your fate.  A judge is probably not really "a peer" and therefore may not give fair consideration to the fact that driving while slightly impaired is not a crime.  After all, millions of Americans drive home after having a drink or two with dinner at the local restaurant.  Are these people criminals under the Kansas DUI statute (K.S.A. 8-1567) if their blood alcohol lever is under the legal limit? I think not.  I think most Americans would view this behavior as not a violation of the statute unless the driver causes a crash or drives in a reckless manner.  But in most cases, a driver is quite "capable" of safely driving after a drink or two.