When can Idaho DUI charges be dropped?

DUI laws in Idaho cannot be dropped unless you convince the court or the prosecutor who is assigned to your case that you really aren't guilty of the DUI or that they don't have enough evidence to prove that you are guilty. Because DUI charges are criminal charges, the prosecutor has a burden to prove your guilt beyond a reasonable doubt. If they cannot do that, either the prosecutor is going to choose not to prosecute the case or the judge is going to dismiss the charges that have been brought against you for lack of evidence (or, if the case gets all the way to trial, then the jury may find you innocent). 

It is important to note that a plea bargain doesn't mean the charges are dropped- it just means that the charges are reduced to lesser charges or that you are given a lesser penalty for the charge that you face. You are still guilty when you arrange a plea bargain, and in fact by definition you are admitting guilt.  As such, the only way to get charges dropped is to:

• Convince the judge or the prosecutor that the evidence against you should not be admissible. Any evidence obtained illegally or in violation of your constitutional rights against search and seizure is going to be suppressed and not used against you in court. This means that if the police didn't have a reason to search you (administer the sobriety test) and they did anyway, the reading on the test that showed your high BAC isn't going to be admissible in court
• Convince the judge or the prosecutor that there is something wrong with the evidence itself. If, for example, the police officer hadn't been properly trained on administering a breathalyzer, then the evidence collected may not be good enough to prove your guilt. 

A good lawyer can evaluate your case and help you to determine if you have any valid defenses or not. Consult with one as soon as possible after your DUI to determine what your options are.