Was there a Cuban gunman in Dealey Plaza?

The new edition of Anthony Summers's JFK book, "Not In Your Lifetime," reports that a man held in a Cuban jail in the 1970s heard from a CIA-supported exile that a mutual friend confessed he was a gunman in Dealey Plaza, according to a story in the British Daily Mail.

This is a substantive allegation, and Summers is careful to report it as such.

The alleg…