Both sides in this wildly strange legal dance are fighting over alleged “unindicted co-conspirator” Vincent Amen.

Amen, I am told, will testify for the defense — if the prosecution agrees that the limited immunity it granted him in December is still active. But that might not be so easy.

Amen’s story makes for a compelling subplot in the Jackson case saga. Sort of an innocent bystander, Amen was brought into Jackson’s world by his best friend, Frank Tyson, who grew up around Jackson.

Amen, now 25, came West to work on Jackson videos and other projects — and wound up babysitting the Arvizo family. He spent more time with them than anyone.

As this column reported a few days ago, Amen actually gave the prosecution team an interview last December. In exchange, he received limited immunity.

But his two-hour interrogation was not what prosecutors wanted to hear. They decided not to use him as a witness for the government.

Now the defense wants to call Amen and invoke the previously offered immunity. District Attorney Tom Sneddon says the deal is off the table.

But late yesterday, right before court was over for the day, Judge Rodney Melville took up this controversy with the jury out of earshot.

The prosecution argued that Amen’s limited “use immunity” would only be good if he had been one of its witnesses.

“But that deal fell through,” Assistant District Attorney Gordon Auchincloss told Melville.

Compounding Jackson’s problems, Auchincloss told Judge Melville that he could get a declaration from John Fahy, the attorney who brought Amen to the December meeting, saying that the immunity idea was only valid for a day.

Note to Auchincloss: Fahy, who was never Amen’s permanent attorney, seems to be off the case. Amen’s original attorney, Michael Bachner, is said to be back in charge. And Bachner’s take on Amen’s off-the-record interview with Auchincloss may be a lot different than Fahy’s.

Meantime, today’s witnesses should be interesting.

Talk-show host Larry King is due to testify that attorney Larry Feldman told him that Janet Arvizo, Feldman’s client, was “crazy and in it for the money.”

What King hoped to achieve when he blurted this statement out to defense attorney Tom Mesereau at the tony Grill restaurant in Beverly Hills is anyone’s guess. Maybe King thinks testifying in Jackson’s defense will get him the first interview if Jackson is acquitted.

King’s lunch partner when Feldman “confessed” was former Dove Audio publisher Michael Viner, the second-most-litigious man in Los Angeles after entertainment lawyer Marty Singer.

Viner, once married to actress Deborah Raffin and the loser of a libel suit against Hollywood madam Heidi Fleiss, thinks he’d be a good witness too.

In his heyday, Viner published books by O.J. Simpson tattletale Faye Resnick and a group of Hollywood professional girlfriends and call girls. More recently, he gave the world Jayson Blair‘s memoir about deceiving the New York Times.

And those are just the highlights.

But today’s very important witness will be Azja Pryor, former fiancée of comic Chris Tucker. Pryor knows more about the Arvizos than anyone. It’s rumored that she will tell stories that could re-curl Michael Jackson’s hair.