Casting a defendant as a dangerous attempted murderer without ever intending to put the defendant on trial for attempted murder would seem like a good strategy for the prosecution for almost any major crime. What are the repercussions that would prevent the prosecution from making allegations that would prejudice the judge against the defendant and hamper the defendant's defense, but never producing a witness at the trial that can be cross-examined?

(My personal guess would be that Ulbricht likely discussed a murder with an agent, but the details of this discussion, whether it was initiated by Ulbricht, and the exact plan the two arrived at are not yet known. I'd also guess that whether or not Ulbricht intended to commit murder, some of these details are ones the prosecution would prefer not to become known for fear that it would damage other parts of their case.)