Can I suggest you look at the work of Ron Blackburn (Aberdeen and Liverpool University Ashworth Hospital) who spent his clinical/academic career in this field including developing psychometric to identify primary and secondary psychopath *SHAPS etc).
I also believe that Karpman was the first one to make that distinction. A really good review is proposed in Patrick's Handbook of psychopathy. Chapter 9 is titled Disaggregating Psychopathy :Where and how to look for subtypes. A section is dedicated to "primary and secondary psychopathy" and reviews the key theories (Karpman, Lykken, Blackburn...) It really helped me! If you don't have access to that book I can scan the pages for you!