Almost inevitably, at some point in criminal proceedings, a defendant will have to enter a plea. Prosecutors occasionally decide not to file charges or to dismiss them at the arraignment or initial appearance, in which case the defendant probably won’t have to plead. (See How should I plead at arraignment?) But defendants who face charges have to plead at least once, in the early stages. (Most cases involve at least two pleas: the initial not-guilty plea, then a plea of guilty or no contest pursuant to a plea deal.)
Some defendants ask to delay plea entry—for example, because they haven't yet been able to hire counsel. And sometimes judges agree. But whether because they’re uncooperative or don’t fully appreciate what’s going on, some defendants refuse to plead.
If the defendant refuses to enter a plea—or to even speak—then the judge will typically enter a not guilty plea on his or her behalf. (The judge may first try to determine why the defendant won’t plead and convince him or her to do so.) Someone who persistently refuses to plead may very well end up in trial, because a plea bargain is obviously out of the question.