PROTECT YOUR EXPERT WITNESSES
In People v. Parson (2008) 44 Cal.4th 332 the court stated that the prosecutor could attack the defense psychiatrist but NOT if the attack was personal / ad hominem and not tied to actually evidence (or reasonable inferences from the evidence).
In Parson, the prosecutor was in bounds arguing the psychiatrist “may have been biased given his status as a paid witness”, but he went out of the evidence and into ad hominem attacks when he called the psychiatrist “a washed-up doctor”.
Remember that in California, a doctor can only give an opinion based upon facts that are IN EVIDENCE. The prosecutor can attack the validity of the data that is IN EVIDENCE but cannot go outside that box.