As soon as the connection between Gibbs and the woman revealed as his ex-mother-in-law was made, Vance should have excercised his authority and excluded him from the investigation. He should not have relied on Gibbs to make that decision. This was not revenge in the heat of the moment but cold calculated murder after many years of careful planning, murder to which Vance was an accessory afte rthe fact. This extremely devious plan is surely beyond her capabilities or is she a secret mastermind of some intelligence agency that she was able to fool two naval officers. Or is this an indictment of a low level of intelligence neccessary in the US Navy and that's not likely.
Further, Gibbs manipulation of Ms. Hart would surely anger her knowing she had been used and thus ending any possilbe relationship between them. Very poor by the writers.
On a separate note, is it only me who is getting fed up with DiNozzo's buffoonery? It's defintely worn thin.