Official Form Interrogatories--General (Disc-001)  prepared by the Judicial Council were intended to be used to cover basic matters as well as being a foundational discovery device in personal injury and contract cases.  They also contained sub-parts which were not allowed when serving special interrogatories and they were not subject to the "Rule of 35".  See California Code of Civil Procedure §§2030.030(a)(2) and 2030.060.  Their use was usually the first volley in the discovery battle.

For years the Courts had found that the Form Interrogatories were objection proof as to form with minor exceptions.  These minor exceptions usually involved case specific issues such as  checking the box with the definition of "INCIDENT" versus creating your own definition for "INCIDENT" and cases which involve complex business transactions.   

Then came the case of Nacht & Lewis Architect, Inc. v. Superior Court (1996) 47 CA4th 214 (pdf) which stated that Form Interrogatory 12.2 which asks: 

"Have you or ANYONE ACTING ON YOUR BEHALF interviewed any individual concerning the INCIDENT? (If so, identify them.)" 

The Third District Court of Appeal found that Form Interrogatory 12.2 was objectionable on the grounds of work product stating:

[c]ompelled production of a list of potential witnesses interviewed by opposing counsel would necessarily reflect counsel's evaluation of the case by revealing which witnesses or persons who claimed knowledge of the incident (already identified by defendants' response to interrogatory No. 12.1) counsel deemed important enough to interview.

For the last 14 years, litigants have objected to Form Interrogatory 12.2 as well as other Form Interrogatories in 12.0 series based on Nacht & Lewis.  However, on March 4, 2010, the Fifth District Court of Appeal ruled in the case of Coito v. Superior Court (2010)182 Cal. App. 4th 758(pdf) that Form Interrogatory No. 12.3 which states: 

“Have YOU OR ANYONE ACTING ON YOUR BEHALF obtained a written or recorded statement from any individual concerning the INCIDENT? If so, for each statement state..." 

was not protected by the work product privilege.  The court stated at pages 768,769:

... witness statements are classic evidentiary material. They can be admitted at trial as prior inconsistent statements (Evid. Code, § 1235), prior consistent statements (id., § 1236), or past recollections recorded (id., § 1237). Yet, if the statements are not subject to discovery, the party denied access to them will have had no opportunity to prepare for their use.   Moreover, a witness statement could contain information favorable to the party denied access, who otherwise could use the statement to refresh the witness’s recollection, impeach the witness’s testimony, or rehabilitate the witness after cross-examination. These impacts on the quest for truth simply are not justified by the policy of encouraging lawyers to prepare their cases for trial or the policy of protecting the diligent attorney from others who would take advantage of his or her industry. (§ 2018.020.) “The purpose of the [work product] doctrine is to prevent incompetent counsel from taking unfair advantage of his adversary’s efforts in preparation for trial, not to suppress relevant testimony which happened to have been obtained by the opposition.” (Jasper Construction, Inc. v. Foothill Junior College Dist. (1979) 91 Cal.App.3d 1, 16 [153 Cal.Rptr. 767].)

With these two cases in conflict with one another, the California Supreme Court has granted review.  In the meantime, Coito v. Superior Court (2010)182 Cal. App. 4th 758(pdf) is not citable pursuant to California Rules of Court.   

I believe that the California Supreme Court will uphold Coito v. Superior Court (2010)182 Cal. App. 4th 758(pdf).   First of all, the basic purpose of the discovery is to take the "game element" out of trial preparation.  See Weil and Brown Civil Procedure Before Trial (TRG 2009) ¶8:1 citing Greyhound Corp. v. Superior Court (1961) 56C2d 355, 376; Emerson Elec. Co. v. Superior Court(1997) 16 C4th 1101, 1107.  Second, knowing whether or not there are witness statements is not protected under a document production as you would have to disclose the information in a privilege log, so why should it be different for interrogatories.  Third, California has a work product statute--C.C.P.  §2018.010 et seq.-- which codifies California law which makes witnesses statements qualified work product.  And, finally, C.C.P §2018.060 allows allows any party to request an in camera review of the documents, which the defendants in Coito v. Superior Court (2010)182 Cal. App. 4th 758(pdf). did not request.    Do you agree?