This reply presumes that Dudley Shonfeld lived and died in NY.
Since he was a person of some celebrity due to the Hauptman trial, I
would look at the index for obituaries which appeared in the NY Times.
Large libraries have this book in the reference section. If he had an
obituary, and it is a good bet that he did, descendants' names would be
This suggestion is in addition to the usual searches of vital records
and census materials.
Good luck, Debbi