Imo, Wonless, it may be a little too soon to conclude that they have bungled this case. Imo, now that the main players have been charged and incarcerated. I feel that the critical tips are flowing in, that may not have been received previously due to the fear of intimidation or retaliation.
There has been a tremendous amount of investigative resources utilized in the 3 year HB investigation to bungle it now, imo.
FYI - Interesting article & stats of prior DP cases prosecuted in TN
http://www.timesfreepress.com/news/2011/oct/16/jesse-mathews-may-face-death-sentence/
Your right about it being to soon to conclude. Just a feeling, for example, the press conference they didn't give the impression of being on the same page about all the aspects of the case, but it could just be that Mark Gwen is only a spokeperson/PR guy and may not know many details. Also the immunity deal with SA coming apart and the fact that JA was charged a month later than ZA. Even in prison, JA could have heard about ZA being charged and gotten a message out to some other person to destory evidence or move the body because somebody in the gang was turning over.
In the end it won't be clear until we see what evidence that happened, and we should be optimistic about the prosecution, but it makes me think things are not going well if there are people involved still on the streets making moves. That's not really clear at this point either.