Credibility determinations are “tasks suited to a jury.” Godinez v. Huerta, 2018 WL 2018048, at *6 (S.D. Cal. May 1, 2018). It is also not, as the County represents, an expert's job to critique the strength of another expert's factual assumptions; allowing otherwise would outsource the jury's role in weighing the evidence.
. Likewise, an expert may not offer legal conclusions “couched in the guise of ‘training[.]'” Godinez v. Huerta, No. 16-CV-0236-BAS-NLS, 2018 WL 2018048, at *6 n. 2 (S.D. Cal. May 1, 2018). As the court in Godinez explained, “[s]uch conclusions are generally not helpful to the trier of fact.
Opinions such as these, separated from what a reasonable officer would do given "applicable procedures and policies," are improper legal conclusions. Godinez v. Huerta, No. 16-CV-0236, 2018 WL 2018048, at *6 (S.D. Cal. May 1, 2018) (excluding Clark's opinions including "judicially defined or legally specialized terms" but allowing Clark to testify about whether a deputy's conduct comported with applicable procedures and policies) (emphasis in original). Moreover, "Plaintiffs concede Clark should not [opine] that, from a causation perspective, Birtcher would not have died if Defendants had followed such training and standards."
Plaintiffs contend that so long as an expert's opinions at trial do not differ substantially from opinions offered in the expert report, they are not late for purposes of Rule 26(a) and therefore are not subject to Rule 37 preclusion. Id. at 4 (citing Godinez v. Huerta, No. 16-CV-0236-BAS-NLS, 2018 WL 2018048, at *8 (S.D. Cal. May 1, 2018)). But Plaintiffs never disclosed Dr. Leff as an expert witness. Plaintiffs' citation to Godinez is misplaced because the plaintiff in that case properly disclosed its expert witness and his report under Rule 26(a)(2).
Further, Defendants argue that Clark's opinions improperly vouch for Mr. Chavez's credibility. The jury must decide credibility, not an expert witness. Godinez v. Huerta, No. 16-cv-0236-BAS-NLS, 2018 WL 2018048, at *6 (S.D. Cal. May 1, 2018). Experts "are not permitted to testify . . . in such a manner as to improperly buttress a witness' credibility."
Despite Rule 26's requirement of a "complete statement" of "all opinions," federal courts generally allow an expert to "supplement, elaborate upon, and explain his report in his oral testimony," as long as he does not provide entirely new opinions that were not disclosed in his expert report. See, e.g., Godinez v. Huerta, No. 16-CV-0236-BAS-NLS, 2018 WL 2018048, at *8 (S.D. Cal. May 1, 2018). Federal Rule of Civil Procedure 37(c) provides two exceptions: (1) when the failure to disclose is substantially justified, or (2) when the nondisclosure is harmless.
Accordingly, courts have excluded expert testimony describing officer conduct as "objectively reasonable" for "using judicially defined or legally specialized terms." Godinez v. Huerta, No. 16-CV-0236, 2018 WL 2018048, at *5 (S.D. Cal. May 1, 2018) (collecting cases). Notably, the Fifth Circuit has held that a police officer is precluded from testifying that a sheriff's shooting of an unarmed suspect was "reasonable" because such testimony would offer a legal conclusion.