Depends, if ya kill ‘em and then cut ‘em up and flush ‘em, they’ll get there without a lot of excavation.
Well, in my book that would be proof that it couldn’t have been an accidental death, because skeleton’s do not break up into small enough pieces that can be flushed down a toilet, can they? It might work to be unidentifiable in a city sewage system where the bone pieces might perhaps be rejected from entering into a sewage processing plant, but certainly not a closed septic system. In either case if the bones are found, accidental death could realistically be ruled out with confidence.🙂👍