Outside of Jefferson’s flunkies...
That's an awfully broad qualifier you use there. In fact, it could apply to over 100 witnesses against Burr in some form or another. The court heard from most of them but it generally did not exonerate Burr by challenging what they said - he got off because none of them could show that he ever ACTED upon his alleged intention of separating the western states - a key legal point, which was also the crux of Martin's defense strategy.
Jefferson dredged the backwoods and taverns for testimony against Burr even going so far as having a questionaire printed and distributed. Of course, not one shred of credible testimony from disinterested sources could be found to show he considered attacking the US much less Wilkinson’s lurid fantasies of murder and mayhem. Even Jefferson knew it was all ludicrous and admitted that he had no real evidence to support the charges. But his persecution was not swayed by considerations of justice.