Which of the following is NOT a plea that a defendant can enter?

The correct answer is that "pro se" is not a plea that a defendant can enter in a court of law. "Pro se" refers to a legal term that describes a person who represents themselves in a legal proceeding without the assistance of an attorney. While defendants have the right to represent themselves (entering a pro se defense), it does not constitute a plea regarding their guilt or innocence in the charges against them.

In contrast, the other options — nolo contendere, not guilty, and guilty — are all recognized pleas that defendants can formally enter in response to criminal charges. A plea of nolo contendere indicates that the defendant does not contest the charges but also does not admit guilt, which can be an important legal strategy in some cases. The "not guilty" plea is the defendant's way of denying the charges, while a "guilty" plea admits to the crime charged. Understanding these distinctions helps clarify the role of legal representation and the nature of the pleas available to defendants.