I referred this discussion to a friend of mine who is a Classic H50 fan, she replied:

Not being a copyright lawyer, I can't give a definitive opinion on this. However, I refer you to this article:

https://www.kashishworld.com/blog/ca...al-characters/

Pay particular attention to the paragraphs involving the two tests of whether a character is copyrightable or not. The character created by John D. F. Black as the victim in "Daisies" may or may not have been "sufficiently delineated" and thus qualified to be copyrightable. A court would have to decide that. As far as I can tell, this could be argued either way.

I don't think the character would pass the "Story Being Told" test, but I could be wrong. The character in question -- J.D.F. Black's Thad Vaughn -- is more a "chessman in telling the story" rather than being the story itself, as required by this test. Anyone would have sufficed as the victim.

But, again, as I am not a copyright lawyer, whatever I offer as an opinion about this must be taken with a grain of salt.