Of course, all trials are "the defendant's trial." But so often what's missing is the defendant. And she is missed.
The privilege against self incrimination formally protects the defendant, and sometimes it actually protects the defendant. Sometimes, however, it does not.
Prosecutors, who would like to cross-examine the defendant, miss her testimony. Jurors, who expect to hear from the accused, miss her testimony. And, of course, the ongoing search-for-truth and aspiration-to-accuracy miss her testimony.
Here, perhaps, is another bargaining chip. The defendant has the right not to testify. She can waive that right. In some cases the prosecution will value that waiver, either because the prosecution believes the opportunity to cross-examine the defendant will benefit its case, or because it believes it favors a fairer and more accurate adjudication, or some combination of the two.
Trial bargains also introduce the possibility of more complex waivers. For example the defendant might waive her Fifth Amendment privilege in exchange for the prosecution agreeing not to introduce prior convictions for impeachment. And if the prosecution values the defendant's testimony enough, it may also be worth conditional leniency.
The point is that within the procedural, evidentiary, and personal confines of any case, there may be room for more bargaining than traditionally occurs. Trial bargaining.