The issue of witness identity surfaces in a number of interesting ways in class actions.  A few years ago, a number of cases examined whether plaintiffs could discovery the identity and contact information of putative class members.  With little qualification, that question was answered in the affirmative (the nature of privacy interests involved define the outer limits on such discovery, but usually yield to the right to obtain discovery of witness identity).  Today, in Coito v. Superior Court (June 25, 2012), the California Supreme Court examined the work product protections applicable to (1) recordings of witness interviews conducted by investigators employed by defendant's counsel, and (2) information concerning the identity of witnesses from whom defendant's counsel has obtained statements. The trial court sustained objections to production of such material, concluding as a matter of law that the recorded witness interviews were entitled to absolute work product protection and that the other information sought was work product entitled to qualified protection.   A divided Court of Appeal reversed, concluding that work product protection does not apply to any of the disputed items.

The Supreme Court held that the correct result is somewhere between what the trial court decided and what the court of appeal decided:

We conclude that the Court of Appeal erred. In light of the legislatively declared policy and the legislative history of the work product privilege, we hold that the recorded witness statements are entitled as a matter of law to at least qualified work product protection. The witness statements may be entitled to absolute protection if defendant can show that disclosure would reveal its “attorney's impressions, conclusions, opinions, or legal research or theories.” (§ 2018.030, subd. (a).) If not, then the items may be subject to discovery if plaintiff can show that “denial of discovery will unfairly prejudice [her] in preparing [her] claim . . . or will result in an injustice.” (§ 2018.030, subd. (b).)

As to the identity of witnesses from whom defendant's counsel has obtained statements, we hold that such information is not automatically entitled as a matter of law to absolute or qualified work product protection. In order to invoke the privilege, defendant must persuade the trial court that disclosure would reveal the attorney's tactics, impressions, or evaluation of the case (absolute privilege) or would result in opposing counsel taking undue advantage of the attorney‟s industry or efforts (qualified privilege).

Slip op., at 2.

The Court went on to analyze first the recorded statements of witnesses collected by an investigator at the behest of an attorney.  Following that analysis, the Court expressly overruled a number of cases on this issue:

In sum, we disapprove Fellows v. Superior Court, supra, 108 Cal.App.3d 55, People v. Williams, supra, 93 Cal.App.3d 40, Rodriguez v. McDonnell Douglas Corp., supra, 87 Cal.App.3d 626, and Kadelbach v. Amaral, supra, 31 Cal.App.3d 814 to the extent they suggest that a witness statement taken by an attorney does not, as a matter of law, constitute work product. In addition, Greyhound, supra, 56 Cal.2d 355, which was decided before the Legislature codified the work product privilege, should not be read as supporting such a conclusion. At the same time, we reject the dicta in Nacht & Lewis, supra, 47 Cal.App.4th at page 217 that said “recorded statements taken by defendants‟ counsel would be protected by the absolute work product privilege because they would reveal counsel's 'impressions, conclusions, opinions, or legal research or theories' . . . . [Citation.]” Instead, we hold that a witness statement obtained through an attorney-directed interview is entitled as a matter of law to at least qualified work product protection. A party seeking disclosure has the burden of establishing that denial of disclosure will unfairly prejudice the party in preparing its claim or defense or will result in an injustice. (§ 2018.030, subd. (b).) If the party resisting discovery alleges that a witness statement, or portion thereof, is absolutely protected because it “reflects an attorney's impressions, conclusions, opinions, or legal research or theories” (§ 2018.030, subd. (a)), that party must make a preliminary or foundational showing in support of its claim. The trial court should then make an in camera inspection to determine whether absolute work product protection applies to some or all of the material.

Slip op., at 20.

The Court then considered discovery directed at the identity of witnesses from whom statements were collected:

The Court of Appeal reasoned that, because the recorded witness statements themselves were not entitled to work product protection, defendant could not refuse to answer form interrogatory No. 12.3. In so concluding, the majority disagreed with Nacht & Lewis, which held that the information sought by form interrogatory No. 12.3 is entitled as a matter of law to qualified work product protection to the extent it consists of recorded statements taken by an attorney. (Nacht & Lewis, supra, 47 Cal.App.4th at p. 217.) Justice Kane, in his separate opinion below, identified a third approach. He would have adopted a default rule requiring parties to respond to form interrogatory No. 12.3, while permitting parties to make a showing that the responsive material is entitled to qualified or absolute protection. As explained below, the approach suggested by Justice Kane is most consistent with the policies underlying the work product privilege.

Slip op., at 21.  The Court considered the various, hypothetical situations where a list of witnesses providing statements might reveal thoughts and impressions.  After discussing the extreme situations, the Court concluded that such discovery should usually be answered:

Because it is not evident that form interrogatory No. 12.3 implicates the policies underlying the work product privilege in all or even most cases, we hold that information responsive to form interrogatory No. 12.3 is not automatically entitled as a matter of law to absolute or qualified work product privilege. Instead, the interrogatory usually must be answered. However, an objecting party may be entitled to protection if it can make a preliminary or foundational showing that answering the interrogatory would reveal the attorney's tactics, impressions, or evaluation of the case, or would result in opposing counsel taking undue advantage of the attorney's industry or efforts. Upon such a showing, the trial court should then determine, by making an in camera inspection if necessary, whether absolute or qualified work product protection applies to the material in dispute.

Slip op., at 24.  The decision was unanimous.

Trial courts should groan in pain at this outcome.  It guarantees that counsel will view their client as having nothing to lose in refusing to provide this information.  Which guarantees that trial courts will have to resolve these fights by reviewing lists of names in camera.  Of course, bad faith refusal to respond will, in the long run, cost parties their credibility with the trial court, but they won't internalize the cost effectively unless strict discovery sanctions are imposed.