A forensic engineering and scientific investigation firm founded in 1987, trading as ESi, working from more than twenty offices across sixteen states with its largest laboratory and testing facility at the founding Aurora, Illinois office. Its fire consultants are stated to meet the qualifications of NFPA 1033 and to follow NFPA 921, and several hold both certifications and a PE licence — Hernán Mercado-Corujo and Scott E. Dillon (PE, IAAI-CFI, CFEI, CVFI), David A. Wilson (IAAI-CFI, CFEI, CVFI) and Amy E. Gray PhD PE CFEI, its technical vice president. The practice pairs origin-and-cause work with failure analysis, fire modelling and courtroom visualisation.