In the case of Victalic Company v American Home Assurance Company the First District Court of Appeal made it very clear that denials to Requests for Admissions are inadmissible.   Here is the court’s reasoning starting at page 23 of the published opinion:

Gonsalves v. Li (2015) 232 Cal.App.4th 1406 (Gonsalves) involved an automobile accident. Plaintiff called defendant as an adverse witness and asked about his qualified denials of plaintiff’s RFAs that he was responsible for the accident. And in closing argument, plaintiff emphasized that the denials were evidence defendant refused to take responsibility for plaintiff’s injuries. (Id. at p. 1413.) The jury returned a verdict for plaintiff for $1,208,642.86. (Id. at p. 1411.) Our colleagues in Division Five reversed, holding it was error for the trial court to allow questions about RFAs.

The court first discussed analogous cases, including Rifkind v. Superior Court (1994) 22 Cal.App.4th 1255, holding

that it was improper to ask at deposition “ ‘legal contention questions,’ ” which questions were condemned as requiring the party “ ‘to make a “law-to-fact” application that is beyond the competence of most lay persons.’ ”

(Gonsalves, supra, 232 Cal.App.4th at p. 1415.) These concerns, the court concluded,

“apply to the use of qualified denials to RFA’s in the examinations here. Li was asked to explain ‘by memory and on the spot’ and without the ability to consult with his attorney why he took the legal position that he could not admit or deny certain RFA’s without further inquiry. And he was asked to do this not in a deposition, as in Rifkind, but in front of the jury.” (Id. at pp. 1415–1416.)

And the court went on to hold: “The weight of authority in other jurisdictions also favors Li’s position. Massachusetts’s highest court interpreted a statutory scheme similar to California’s and concluded that denials to RFA’s are not admissible evidence at trial: ‘The purpose of [RFA’s] is to narrow the issues for trial by “identifying those issues and facts as to which proof will be necessary.” [Citation.] A denial . . . is not a statement of fact; it simply indicates that the responding party is not willing to concede the issue and, as a result, the requesting party must prove the fact at trial. [Citations]. The sanction for improperly responding to [RFA’s] is the shifting of the award of incurred expenses[—see rule 36(a) of the Massachusetts Rules of Civil Procedure]. [¶] Further, [Massachusetts Rules of Civil Procedure, rule 36(b)], which governs [RFA’s], does not specifically provide for the admission of denials in evidence. Although the rule states that admissions are conclusively binding on the responding party, it makes no parallel provision for the use of a denial. By contrast, [Massachusetts Rules of Civil Procedure, rule 33(b)], governing interrogatories, states that the answers to interrogatories “may be used [at trial] to the extent permitted by the rules of evidence.” The omission of a similar provision in rule 36(b) indicates that, although admissions have binding effect, denials do not have such an effect and cannot be introduced in evidence.’ [Citation.] Therefore, the trial court ‘incorrectly concluded that a denial of a request for admission is admissible as a prior inconsistent statement’ to impeach a witness at trial. [Citation.]” (Gonsalves, supra, 232 Cal.App.4th at p. 1416, fns. omitted.)

Finally, Gonsalves noted that appellate courts in at least three states have similarly held that denials of RFA’s are inadmissible at trial, citing to Winn Dixie Stores, Inc. v. Gerringer (Fla.Dist.Ct.App. 1990) 563 So.2d 814, 817; Mahan v. Missouri Pacific Railroad Co. (Mo.Ct.App. 1988) 760 S.W.2d 510, 515; and American Communications v. Commerce North Bank (Tex.App. 1985) 691 S.W.2d 44, 48.) (Gonsalves, supra, 232 Cal.App.4th at pp. 1416–1417.)