Karma is actually the Law of Cause and Effect. Where the mysticism comes into it is the artificial construct of magnification of one action causing a threefold return of action, without any scientific validation of such a result.
If you punch me the odds are I'll deck you beck. Whether I knock you out and then two other actions come along to counter your initial action is not something one can scientifically verify will happen.
The initial cause may have your perceived original effect, but you have no control over the effect(s) resulting in your causal action.
I think people are getting way out of their field of expertise here.
FWIW, Karma is not a cosmic system of justice, but simply translates to your own 'doing'.
There is nothing but a single, unified existence in which we're all 'god' playing a multitude of parts in a cosmic game of hide and seek. If we are all god, then anything you do, you're doing to yourself.
Its been corrupted to mean cosmic payback.