What Happens in a DUI Trial?
Once the jury has been selected, the parties to the DUI case have an opportunity to make their opening statements. Since the prosecutor has the burden of proof, he gets to go first (he is the only one in the "proving" business; the defendant has no obligation to prove anything). After the prosecutor gives an opening statement, the defense lawyer has the choice of giving his or her opening statement at that time, or of reserving the defense opening statement until after the prosecutor has concluded his case. Generally, the defense lawyer will give their opening statement right away, so the jury can have the defense views in mind when they are listening to the prosecution's case.
The judge typically indicates to the jury that what the lawyers say is not evidence, that they are simply forecasting what they expect the evidence to be, and that counsel is not permitted to argue the case at that time. The experienced DUI defense lawyer will seize the opportunity, and argue the hell out of their case.
Experienced DUI defense lawyers are righteously cautious about this very important phase of trial. Often, it is not known exactly how certain aspects of the case will play out; any promises that are made in the opening statement and not delivered upon later in the case will certainly be brought up by the prosecutor. It may not yet be clear whether the defendant will testify. Often, the most compelling evidence will arise only from cross-examination of the arresting officer or prosecution expert, and the details won't be known when the opening is made.