Makes me think they don't have any DNA evidence or other physical evidence that ties anyone to her murder.
I agree, SteveP, that this could very well be a solid indication that the DNA evidence was either nonexistent or not helpful, and we all know what happened with the other physical evidence, so there's no need to rehash that for the umpteenth time... but, on the bright side, I have seen convictions on murder cases where there wasn't even a body, let alone DNA evidence, so I am keeping my fingers crossed that the FBI/DEA/ATF are building an otherwise strong case, and are just seeking that one witness to come forward to corroborate. Further, I have seen that once one witness comes forward, they start falling like dominos. Fingers crossed this is the case here!