Start with the registry, not the brochure. The U.S. Green Building Council maintains a public project directory where LEED certifications can be searched by project name or ID; BREEAM, Green Star, and the Passive House Institute operate comparable databases. A genuine certification resolves to a specific record with a date, a level, and a scope.
Next, separate the three kinds of claims that listings blend together: organizational membership in an industry body, individual staff accreditation, and certified project outcomes. Only the third certifies a building. Finally, check recency — ask when the listing was last updated and whether the cited projects are complete. Credentials that cannot be traced to a registry entry should be treated as marketing language, not evidence.