I agree with someone else earlier that Becky's bedroom seems too immaculate (by way of blood splatter) for the actual murder to have been committed inside her bedroom. I somehow don't buy that unless they prepped the place with covers. There are signs of struggle, yes, such as the broken shelves were as is, and not damaged by forensic investigators. But there appears, based on the description, to have been very little blood splatter other than a bloody fingerprint belonging to the male victim.
However, the fact that the forensic pathologists noted the victim sustained multiple stab wounds while she was still alive, this would probably have left a mess. Something might be amiss here. A clearer chain of events describing the physical altercation might be helpful.
The toilet where they allegedly did the disposal is cluttered with crap just besides the bathtub. Either they prepped the place, or else there must be physical evidence like blood splatter or tissue matter left on the items there. I also doubt they actually used much of the circular saw. Its a powerful tool and there will be lots of mess. Also, did they somehow drape the bathtub? Because otherwise, investigators should have taken the pipework to do testing on it, as evidence will surely have trickled their way down there if the suspects simply flushed away some residual evidence and cleaning solution.
