If there is no reasonable doubt to a jury that the Chief in fact knew in his own mind that the mailbox thief in the video was not really his wife's uncle, then failing to otherwise supervise his CIU can legally amount to criminal conspiracy.  Tacit understanding evidenced by acts of commission or omission by chain-of-command authorities is enough to present criminal conspiracy to a jury.  Face to face clandestine meetings and plotting are not necessary.