Confidentiality is a critical topic, especially in mediation which appears informal.  In California, everything spoken or written in a mediation is strictly confidential. (Evidence Code 1119).  The California Supreme Court rejected "acting in bad faith" as an exception to this confidentiality (Foxgate).  In a court annexed mediation, the lower court pierced a mediator's confidentiality after a plaintiff complained that the defendant obstructed the mediation process.  The Supreme Court of California rejected this intrusion. (Foxgate).

But what about physical evidence that has been produced especially for a mediation?  The California Court of Appeals held in a 2002 decision (Rojas) that photographs and videos were not protected.  The attorney work product privilege may provide some protection, but if the evidence prepared for the mediation and the work product is amalgamated enough, the court may lift the veil of protection! The attorney work product doctrine was proposed as the test for determining the extent of the protection. If the evidence prepared for mediation would count as "raw evidence" of "derivative evidence" under the work product standard, then the evidence would be discoverable (only on a showing of good cause for "derivative evidence", which the court found to exist because there was no other evidence of the construction defects). Whether the result in this case is limited to it's specific facts (ultimately in favor tenants), remains to be seen.

The federal court of the Northern District of California ruled that the state's contractual arbitration standards are preempted by the Federal Arbitration Act and Exchange Act. (Mayo v. Dean Witter)

The California Supreme Court ruled that the evidence spoken or written in connection with a mediation proceeding is non-discoverable and inadmissible by reason of the mediation confidentiality statutes, even for the purpose of proving a malpractice claim. (Cassel case)

Foxgate case
Mayo case
Rojas case
Buckeye case
Cassel case