It can be shown in trial against Nifong (and a separate one against the accuser, if need be) without putting the boys in jeopardy. It's sort of analogous to taking the WoT to the ME, such as Iraq, instead of letting the enemy come to our soil. :)
Nifong has already admitted that the only evidence he has is the accuser's statements, which are dissolving, yet the risk of a racist jury of black Durhamites deciding they want to convict no matter how obvious their innocence is is great. If it was your son, would you take that risk, especially when it has become obvious anyway to every sentient person that he is innocent? You'd risk him being sentenced to forty years in prison by a bunch of racists? No defense attorney worth a dime would allow that if avoidable.
The most essential flaw in this case has been NC criminal procedure. There is no mechanism for a probable cause hearing. If there was, it would have been apparent long ago that Nifong did not have anything remotely approaching the needed elements to even show that a crime occurred, let alone that these boys committed it. In a probable cause hearing, Nifong would have had to set forth what he claims happened, who did what, when, where and how. The lack of evidence, multiple stories and alibis would have come in and blown him out of the water, and probable cause is a lesser burden than beyond a reasonable doubt. In a normal state, Nifong would first have to show that a crime occurred, but that's not the case in NC because of the way the law is (or isn't) structured, and that includes their hokey indicting grand jury system.