An opponent has the right to depose a testifying expert (after the report is issued) under Fed.R.Civ.P. 26(b)(4)(A) but may depose a non-testifying expert only in “exceptional circumstances” under Rule 26(b)(4)(B). What if a testifying expert is later re-designated a non-testifying expert? What test is used to determine whether the re-classified witness may be deposed? Or whether that witness is subject to documentary discovery? There is a split in the caselaw, which is discussed in Federal Ins. Co. v. St. Paul F & M Ins. Co., 2008 U.S. Dist. LEXIS 25927 (N.D. Cal. March 19, 2008). Federal determined it appropriate to apply the “exceptional circumstances” test rather than a balancing test:

This court agrees that Federal Insurance is no longer entitled to depose Dr. Hillman under Fed. R. Civ. P. 26(b)(4)(A). Moreover, it appears that the majority of courts that have confronted this issue have concluded that the "exceptional circumstances" standard applies. See Estate of Manship v. United States, 240 F.R.D. 229, 235-37 (M.D. La. 2006) (reviewing cases). Accordingly, this court concludes that the "exceptional circumstances" test should be used here.

Even so, Federal Insurance emphasizes that Dr. Hillman's expert report was produced before St. Paul re-designated him as a non-testifying expert. Indeed, several decisions suggest that discovery of a withdrawn expert should be permitted where that expert provided testimony or produced a report before re-designation. See e.g., Estate of Manship, 240 F.R.D. at 237 (concluding that exceptional circumstances did not exist to justify a deposition where the experts would not testify at trial and did not produce expert reports); Ross v. Burlington Northern Railroad Co., 136 F.R.D. 638 (N.D. Ill. 1991) (concluding that the protections of Fed.R.Civ.P. 26(b)(4)(B) for non-testifying experts were not waived where nothing more than the identity of the expert and the subject matter of his testimony was revealed); see also CP Kelco U.S., Inc. v. Pharmacia Corp., 213 F.R.D. 176 (D. Del. 2003) (holding that where the attorney-client privilege was waived when defendant produced certain documents to its expert witness, defendant was required to produce those documents to the opposing party, notwithstanding that after the expert's deposition, defendant decided to re-designate the expert as a non-testifying consultant).

Held, no discovery — oral or written — of re-designated expert permitted.