According to John Atack, Hubbard cribbed most the the SP data from
The Mask of Sanity by Hervey Cleckley, M.D..
(According to Piece of Blue Sky:
http://www.cs.cmu.edu/~dst/Library/Shelf/atack/bs4-1.htm)
That book is available for download as a pdf from here:
http://www.cassiopaea.com/cassiopaea/psychopath.htm
Cleckley lists on p. 338/9 the characteristic points below, and in the subsequent pages amplifies the points, but less than a page each so it's not a whole lot of reading to do. I've numbered his points and compared them to Hubbard's. It's not a good match at all.
C1. Superficial charm and good "intelligence" [no match]
C2. Absence of delusions and other signs of irrational thinking [no match]
C3. Absence of "nervousness" or psychoneurotic manifestations [no match]
C4. Unreliability [no match]
C5. Untruthfulness and insincerity [no match]
C6. Lack of remorse or shame [=H8]
C7. Inadequately motivated antisocial behavior [no match]
C8. Poor judgment and failure to learn by experience [no match]
C9. Pathologic egocentricity and incapacity for love [no match]
C10. General poverty in major affective reactions [no match]
C11. Specific loss of insight [no match]
C12. Unresponsiveness in general interpersonal relations [no match]
C13. Fantastic and uninviting behavior with drink and sometimes without [no match]
C14. Suicide rarely carried out [no match]
C15. Sex life impersonal, trivial, and poorly integrated [no match]
C16. Failure to follow any life plan [=H7 somewhat]
Hubbard lists the characteristics of an SP as:
H1. Speaks in generalities [no match]
H2. Deals in bad news and invalidation, no good remarks [no match]
H3. Stops good news; relays/worsens or invents bad news [no match]
H4. Doesn't respond to treatment, reform or psychotherapy [no match]
H5. Surrounded by cowed, ill associates or friends [no match]
H6. Selects the wrong target [no match]
H7. Can't complete a cycle of action [=C16 somewhat]
H8. No remorse or shame [=C6]
H9. Supports only destructive groups; against constructive groups [no match]
H10. Supports only destructive actions; against constructive actions [repeat of H9! no match]
H11. Helping others drives him berserk; can only destroy in the name of help [repeat of H9! no match]
H12. Bad sense of property: no-one owns anything [no match]
So unless I'm missing something here, Hubbard didn't rip off those points mainly from Cleckley.
Paul