It ain't libel unless he knows (or has reason to believe) it's untrue. And I do believe that Fatty, like the majority of people here, honestly believes that Chico killed her
based upon their histories and the available facts.
In any event, in this country, he's got every right to put forth any theory he likes. People still speculate about OJ nearly 15 years later.
You might want to read up on it.