TMZ was in the courtroom just minutes ago when K-Fed's lawyer said the "secret witness" in the case is an employee of Britney's -- after she left rehab.
Dennis Wasser, who reps Spears, said, "Shame on Mr. Kaplan. How can he let this go on?" We're told Kaplan made a play for the witness last Tuesday, but was shut down by the judge.
Gloria Allred, who reps the witness, is about to address the court and explain why the judge should consider his testimony in the custody dispute.
Then the judge threw us out and made the proceeding itself secret!
Stay tuned ...