It would be incompetence if they hadn't used the "latest forensic techniques" in their search for evidence, and if such techniques had failed to produce any evidence, I don't see how one could blame the police for that. But most importantly; you have no idea what evidence they found. None of us do.
You state that A&SC "pursued one suspect with so much vigour", and that VT "must have had a cast iron alibi" and was "eliminated from their enquiries" when he was "interviewed early on". You state all these things as if they were facts, when they're really nothing more than part of the script that you've written in your head. You have no idea as to when VT (or indeed anyone else for that matter) was first interviewed by police, you have no idea what questions he was asked, what his responses were, or what conclusions were reached as a result.
Incidentally, cadaver dogs are trained to detect decomp. It normally takes about three days for putrefaction to set in, and for decomp to be present. So they're of no use whatsover unless you've got a corpse that's been dead for that long. If (and it's a big if, since proceedings are active and so forth) VT was the culprit, then the corpse would have been dumped well before that, and thus the cadaver dogs would have been quite useless. And just because there haven't been any press reports of cadaver dogs present at Canynge Road, that doesn't mean to say that they weren't there at some point.
I tried to put the two Post's up as a double quote the Poster you spoke to, I could not make them both come up only your's.
I agree none of us know what the A&S know, what the Forensic evidence is, and what they have on VT, the A&S must have something substantial for the CPS to go ahead and the two Court appearances so far.
I did wonder about cadaver dogs in all this, and we have never seen any dogs being taken into the Flat's, if this was done I do think the Media would have been there ready to Broadcast about the dog's, it could have been done away from the Media though, however the Media were present outside the Flat's for some time.
I have written below about cadaver dog's and the time it takes to mark and scent where a body has been in situ, then the body has been removed, that makes in IMO that the A&S knew JY was not kept in the Flat's anywhere, or in an outside shed for a long period of time, because the dogs would mark that Area if she had been placed there, and that perhap's A&S knew this and that JY was moved quite quickly after her demise, although the dogs could have been taken in on the quiet, although I can't see why the A&S would want to hide a cadaver dog being taken into the Flat's, and surrounding Area.
Cadaver dogs and marking/scenting.
After death body temperature begins to drop chemical changes in muscles begin and autolysis advances, this is the odour that the cadaver dog mark's, the body temperature has to start to drop then continue to drop, for the chemical changes to take place, the start of the autolysis start's after one and half Hour's to two Hour's after death, then if JY was placed somewhere after the autolysis advances started one and half to two Hour's after her demise, then the dog would mark that Area, it does not take day's for the odour to start.