Hearing the phrase "pre-trial motions" probably doesn't elicit a lot of excitement out of you, and that's understandable. They sound boring and listless. But, in truth, pre-trial motions are incredibly important in criminal cases, and they can be absolutely critical in drunk driving cases. This is because the pre-trial motions can actually dictate how a case is handled at trial.
Pre-trial motions generally handle three things: the physical evidence that is allowed at trial, the legal arguments that are allowed at trial, and the topic of whether the defendant should even have to stand trial.
Knowing this, you can see why pre-trial motions are so important. If you are accused of a DUI, these motions hold a lot of power. The argument could be made that certain pieces of physical evidence should not be allowed in the trial. If upheld, that could ruin the prosecution's case.
A defendant and his or her attorney could also argue that the defendant's Miranda rights were violated, or that the police acted inappropriately during the course of the investigation. Other pieces of evidence could also be contested in pre-trial motions, such as breath or blood test results.
There is a very simple lesson in all of this: even the most mundane (or, more accurately, the most mundane-sounding) legal steps are incredibly important in criminal cases. If you have been accused of a drunk driving offense, or any criminal offense for that matter, you need to consult with a criminal defense attorney.
Source: FindLaw, "DUI Pre-Trial Motions," Accessed March 2, 2016