Everything the defendant said is still governed by the same rules of evidence that determine what can come in at trial.
The defendant's words must be admissible for a reason.
Thus, the interpretation that everything goes in, as stated, might be just a little bit too broad.
That said, all the witnesses, are going in with their 5th amendment privilege tucked inside a pocket. Casey can remain silent already.
Other witnesses can refuse to answer the prosecutor on the grounds it may incriminate them. Caveat: Unlike the right of Casey to say nothing and remain silent,
Witnesses cannot invoke that 5th amendment privilege just to get out of testifying about things that make them uncomfy or things they don't want to talk about.
It has to be a legitimate concern about self-incrimination, with an actual basis.
The Judge will have the final call about that and not the actual witness.
So not to worry, if the self-incrimination clause is utilized as an escape method to avoid testifying, it won't work and a Judge will order the witness to testify.
jmho