wow. thanks for the quick replies.
children as culprit? always possible, but we have had alot of experience as foster and adoptive parents and my wife has an exceptionally developed (and possibly scary) intuition and ability to read people, especially her own family.
she is certain that it is not one of them. also there is a pretty clear pattern of correlation between incidents with the suspect and a dead chicken. also, in fostering the level of care advertised is never what you get.
we have in the last few months been given a real trail cam and I have cobbled one together from a little project computer called a Raspberry Pi. (works great by the way, just sayin')
only two cameras in operation with no results.
the dogs all sort of recreate by chasing large birds before they can land: vultures, hawks whatever. its their countrified version of chasing the mailman I suppose.
all the chickens were killed inside their particular areas. too small to be called free ranging, but it is what it is. as to motive? the suspect is absolutely bonkers ( to use nice words and stay away from obvious psychological labels)
we do butcher the meat birds, if it was a child I would expect they would try to emulate that rather than consistently go to the same method.
we live on 55 acres almost in the middle of nowhere. our nearest neighbors are about 1/2 mile away. no joggers ever spotted, though sometimes those people can get a little carried away

basically, we're out in the boonies.
I know that it is almost certainly the suspect in question. I just wanted to get an idea of how often chickens actually break their own necks.
Thanks again!