I have no reason to doubt the integrity of the CCP or Arpaio or Gallup. I can imagine that if some information were to be released before certain procedures are in place could jepordise the evidence and or give certain people a window of opportunity. We just don't know.
Which is why it is so unprofessional for a supposed law enforcement agency to make an announcement that they will be unveiling earth-shattering evidence on March 19. If they have definitive evidence of a crime, they have a duty to act on it now and not wait. If they do not have definitive evidence of a crime, they have a duty to keep silent, for the protection of the innocent, until they do.