Backstab hit detection

[Ommamar]

I saw another thread that talked about how hit detection worked for archery but I am not sure how that works for backstab skill. I know there is a roll involved but a lot of times when I use invisibility to get behind the target I don't get a backstab. If I am positioned to the side or even in front sometimes I will, it isn't a hundred percent of the time and I have gotten a backstab from behind. More often though I will get behind swing either miss entirely or just do a regular hit then when they turn to face me I get a backstab. I don't know if there is some delayed reaction but it is odd to see backstab successful when the target is facing me.