Generally depositions of adverse experts are taken only after the exchange of expert witness information pursuant to California Code of Civil Procedure section 2034.210 (see CCP 2034.410). Notwithstanding that general rule, you may take the deposition of an adverse expert witness if the adverse expert witness has provided his/her testimony prior to the exchange of expert witness information. Specifically, we have on occasion experienced that plaintiff's expert would provide a declaration in opposition to our client's motion for summary judgment. Normally we would file an Evidentiary Objection to such a declaration for a host of reasons (which we will discuss in a future blog). For now, if you believe it would be strategically advantageous to take this expert deposition you can do so.
It is important to understand the reasons why. A witness is a witness; you can depose anyone with relevant info unless the witness enjoys some protection against disclosure of the information. Ordinarily, expert depositions do not occur during the percipient phase of discovery for two reasons:
1) You may not even learn the identity of an opposing expert until 2034 designations are served;
2) But even when you learn the identity, you cannot compel the expert to disclose opinions in deposition until:
a) He has been designated per CCP 2034.210, or
b) When his/her opinions have been volitionally offered via deposition testimony, trial testimony, or (as in our case) declaration.
A retained expert is merely a consultant (cloaked with work product protections) until he/she is designated, or until he/she voluntarily discloses opinions (thereby waiving the protections). Indeed, a party can designate an expert, then withdraw that designation (so as to prevent disclosure of opinions) so long as this withdrawal occurs before the opinions are actually disclosed. In Shooker v. Sup. Ct., this withdrawal occurred DURING THE EXPERT DEPOSITION but before opinions were disclosed; the court of appeal held this withdrawal timely.