Kennedy v. Joy Techs., Inc., 2008 U.S. App. LEXIS 5396 (4th Cir. March 12, 2008) (unpublished) summarizes caselaw holding that Federal Rule of Evidence 803(8)(C) places the burden on the opponent of admissibility of an official record to establish its lack of trustworthiness, absent which admissibility is presumed. The opinion also usefully identifies the sorts of factors opponents should focus on:

Under Rule 803(8)(C), the evidentiary admissibility of public records and reports is deemed to be presumed, based on the policy determination that such admissibility is warranted "because of the reliability of the public agencies usually conducting the investigation, and their lack of motive for conducting the studies other than to inform the public fairly and adequately." Ellis v. Int'l Playtex, Inc., 745 F.2d 292, 300 (4th Cir. 1984) (internal quotation marks omitted). As the Supreme Court has recognized, "portions of investigatory reports otherwise admissible under Rule 803(8)(C) are not inadmissible merely because they state a conclusion or opinion." Beech Aircraft Corp. v. Rainey, 488 U.S. 153, 170, 109 S. Ct. 439, 102 L. Ed. 2d 445 (1988). When the trustworthiness of such an investigative report has been challenged, a court should assess and weigh factors such as: (1) the timeliness of the investigation; (2) the special skill or experience of the investigators; and (3) any possible motivation problems. Ellis, 745 F.2d at 300-01. We have also identified other factors that may, in the proper circumstances, be appropriate to such an evidentiary assessment, including "unreliability, inadequate investigation, inadequate foundation for conclusions, [and] invasion of the jury's province." Distaff, Inc. v. Springfield Contracting Corp., 984 F.2d 108, 111 (4th Cir. 1993).[Brackets in original]

The key word in this passage is in the first sentence: “presumed.” Held, the District Court abused its discretion in excluding from evidence a portion of the accident investigation report made by the Mine Safety and Health Administration concerning the death of the plaintiff’s husband because “[f]irst foremost, the court failed to recognize and apply a presumption of admissibility to the MSHA Report. As we recognized in Zeus Enterprises, Inc. v. Alphin Aircraft, Inc., ‘[t]he admissibility of a public record specified in the rule is assumed as a matter of course, unless there are sufficient negative factors to indicate a lack of trustworthiness.’ 190 F.3d 238, 241 (4th Cir. 1999) (internal citations omitted). Furthermore, the party opposing the admission of such a report bears the burden of establishing its unreliability. Ellis, 745 F.2d at 301. Thus, Rule 803(8)(C) ‘is not a rule of exclusion, but rather is a rule of admissibility,’ so long as the proffered report satisfies the requirements of the rule. Zeus, 190 F.3d at 241.”