Legal Question in Legal Ethics in California

No. The case is over, and you lost. You lost because you tried to play amateur lawyer and do your own medical malpractice case.

It is not clear from your post whether you intend to file a new lawsuit against the original defendant doctor, or your own retained medical expert. The answer, however, to both issues is, no. People have immunity pursuant to Civil Code section 47 for statements made while testifying as witnesses. The policy behind this rule is to allow people to testify freely, without the threat of subsequent civil lawsuits.

Mr. Roach and Mr. Stone are both right. Everything said in a case is privilged, and you didn't lose the case because of what the Dr. Said, you lost because you were in pro per and had no idea how to handle a malpractice case.