Aloha1935 has pretty well put this in perspective. Unfortunately, those living in the western world do not give much thought, if any, to the laws of karma. In the bible it states,"as you sow, so shall you reap", but it is rare to hear any preacher speak on this subject, mainly because they know nothing about it.
Most eastern religions give great importance to karma. What ever you do in this lifetime you will pay for it in some way in the next. So all the crimes you committed in previous lives, in the 1400's or whenever, you will suffer in some way. It may take several lifetimes before you are free of this suffering. As you are aware of your previous mis-deeds, you can help yourself by performing only good and beneficial works and most importantly, by serving God.