If this mom had nothing to do with it but then finds herself in the position of having failed a polygraph and being straight up told by police that "you did it", then wouldn't you expect her to stop cooperating with the very people that are pinning this on her.
I have to say, I have always wondered whether or not I could pass a polygraph, and I am a ridiculously honest person. But I also know of myself, that I often feel guilty or bad for things I did not do if I can't prove I didn't do them.
For instance, my cousins garage was broken into years ago and my husband had the key to the garage. When my cousin came home he dared ask us about it and "jokingly" mentioned my hubby having the key. While I know deep down he knew my hubby didn't do it, and we eventually found out who did... there was a moment there where it was like I was in the position of having to prove a negative....that is a very hard thing to do. I honestly wonder how I would have done on a polygraph at that time even though I knew I/we/he had nothing to do with it. Is it just me, or is anyone else like that?
While I am super suspicious of this mom, I am really hoping she had nothing to do with it and just has no way to prove that.
Maybe someone with experience in polygraph can tell me if there is a "type" of person who may not pass even if they are innocent.