What are the differences in pleading guilty and no contest in a DUI case?
The purpose of entering a no contest plea is to try and avoid being sued in civil court for confessing to a crime (unlike a guilty plea). In other words, pleading no contest can restrict someone from automatically gaining leverage in a civil suit. On the other hand, a guilty plea means you admit to the charges, have no defense for your actions and the court can go ahead and pronounce a sentence on you.
When a person pleads "nolo contendere" (i.e. no contest) they do not admit guilt but the court can still determine the punishment. The judge will question the defendant to make sure that they understand the plea and its possible consequences. This gives the defendant an opportunity to explain the circumstances of the incident. The judge then gains a better understanding of the situation, which can mean that the defendant has the possibility of getting a more lenient sentence than otherwise might be might handed down.