On page 94 in the Kindle edition of Cyril Wecht's book, he writes:
"In 1963, Victor L. Marchetti, Jr., was a CIA agent specializing in Cold War espionage but would later quit and write books that were critical of the U.S. intelligence community. Marchetti described how the Office of Naval Intelligence established a program where several dozen young American men were assigned to appear disenchanted about the United States and would be sent into Russia or Eastern Europe. Their goals was to be recruited as KGB agents, but they'd actually function as "double agents," since their true loyalties would remain with America. The men were trained in U.S. Naval installations abroad. At the Marine base in Atsugi, one of Oswald's case officers was Gerry Patrick Hemming, who had worked for Fidel Castro as a CIA double agent, then turned virulently anti-Castro once he left Cuba. Was Oswald part of the ONI program Marchetti described, and was Hemming his handler?"
I have seen no evidence anywhere that Gerry Patrick Hemming was Oswald's handler. He's long been known as a loose cannon in the JFK assassination world and most people do not take him seriously.
There is also no evidence that Hemming had any association with the CIA.
By the way, there are no footnotes for Wecht's book.
I discussed Hemming in my book, I Was a Teenage JFK Conspiracy Freak, in a section about a Canadian Broadcasting Corporation documentary on the JFK assassination: (pages 181 - 184)
The most sensational part of Dallas and After is when Adrienne Clarkson talks to Gerry Patrick Hemming, an ex-Marine soldier of fortune who was involved in the fight to overthrow Castro. He told The Fifth Estate a wonderful story indicative of a healthy imagination. Here’s the complete discussion:
Hemming: I’d been to the White House earlier that year [1963] in March. I was in the east wing of the White House having an interview with the military aide to the President, General Clifton. I’d been to the Pentagon, the State department, what have you earlier in 1963. I’d done quite a bit of travelling. Had new contacts, dealt with very prominent people and in travelling I heard constant comments as to a solution to the Kennedy problem. It got very serious as to why uh waste time in Cuba. Why risk lives. The whole problem is in the White House. That should be taken care of.”
Adrienne Clarkson: Did someone walk in with a case of money and ask you to kill John Kennedy?”
Hemming: Well only one time was there money on the table. All other times we got out of the conversation and out of the meeting gracefully enough to avoid discussing any figures. Obviously these people had uh they’d been recommended to us and we’d been recommended to them and now suddenly we were discovering why these recommendations had been made and why these introductions had been made.
Clarkson: What kinds of techniques were discussed?
Hemming: Just proper standard techniques.
Clarkson: Such as?
Hemming: Sniper’s techniques, explosive techniques. Remote control explosive devices. Shooters.
Clarkson: Do you think number of different groups were putting out a contract on Kennedy’s Life?
Hemming: That was the feeling we had before Dealey Plaza. My name was thrown into the mill and into the Warren Commission right off the bat. I was prime shooter. My crew was the only capable team in the whole United States of America. This was from day one this was pushed. And it upset me to a great degree and I’ve made it a point to find out who did what who didn’t do what in the last 14 years. I’ve answered a lot of questions myself.
Clarkson: Answer me one. Who did it. Who did the job?
Hemming: I know personally of more than one group of individual that collected money and they ripped them off. They didn’t do the job. They took credit for it. Well they only, they’d taken money beforehand. Stroke of luck for them.
Does any of this make any sense? Tantalizing clues about absolutely nothing.
Less than six months later, Hemming testified before the HSCA. His first-hand story morphed into “offhand remarks” at a meeting in Dallas sometime in 1962 which Hemming characterized as “loose conversation.” It took up less than a page in a deposition of 200 pages, and Hemming wasn’t even mentioned in the HSCA Final Report.
Over the years, Hemming’s spiel has included more and more characters from the assassination saga (Oswald, Ruby and others), he was willing to tell stories to any researcher and any JFK conspiracy group with the time to listen. The 1996 JFK Lancer conference convened a panel discussion with him, and researcher John Kelin wrote that “as far I could tell, [he] provided little more than a measure of comic relief.” He elaborated that “we were not, however, treated to many serious answers during the hour or so the panel lasted. In fact, many of his answers were couched in sarcasm, and somewhat condescending irony.” Hemming went on to charge that Oswald was following him around at an anti-Castro training camp near Lake Pontchartrain, north of New Orleans. The moderator asked Hemming, “What would you perceive to be the purpose, or function of Oswald being on your tail?” He answered, “They [the anti-Castro Cubans] pegged him as a Soviet agent. Who knows what’s in these peoples’ heads, what they had him doing. I want you to penetrate these exile groups, kid, and I’ll give you an extra Snickers bar.”
Hemming also hung out on JFK assassination bulletin boards on the Internet. He was asked about his interview in Dallas and After in 2006 and he disputed the accuracy of the transcript. He wrote that “The CBC lady who was doing the interviewing…she didn’t know sxxx-from-Shinola, and I quickly became aggravated that she hadn’t a clue about the subject matter.” Hemming died in 2008 and will forever remain a small footnote in the JFK assassination.