I believe it would be inadmissible hearsay if Cohen (or another witness) were to testify "CA told me he was being extorted by KM." Under FL law, hearsay "is a statement, other than one made by the declarant while testifying at the trial or hearing, offered in evidence to prove the truth of the matter asserted." Fla. Stat. 90.801. CA would be the "declarant" here. And the defense would be offering the statement "to prove the truth of the matter asserted," i.e. that KM extorted CA. So Cohen (or anyone else) could testify that he witnessed the extortion directly, but not about what CA told him about the extortion.
All that said, one thing I've been struck by during the trial is how neither side is making much of an effort to hold the other to the rules of evidence. The prosecution's questions have been blatantly leading. Witnesses have been testifying to things without adequate foundation. Tons of hearsay has come in. But objections from either side have been rare.