In aviation and automotive crash scenarios, head injuries are the most severe and fatal type among all the injuries incurred to the occupants. Head injuries typically occur when the head of the occupant comes in to contact with any aircraft cabin interiors, bulkheads, car steering wheel, windshield, etc. The compliance with the Head Injury Criteria (HIC) regulatory requirement is a significant concern for aircraft and automotive industries due to the importance of occupant head injury protection as well as the cost associated with the certification. The objective of this research is to examine various factors that might influence the resulting HIC value in both automotive and aircraft crash scenarios. A Hybrid-III free-motion headform (FMH) model is utilized for this purpose to investigate the variations of the HIC with different combinations of the target conditions (material, thickness, boundary conditions, and friction, etc.), as well as the impact conditions (impact velocity and impact angle). All the computational impact simulations are conducted in the LS-DYNA Finite Element (FE) software. A parametric study is then carried out using the Taguchi methodology and design of experiments (DOE), with combinations of different target and impact conditions. The analysis of variance (ANOVA) approach is utilized to study the relative percentage contribution of these conditions on the resulting HIC evaluation. The sensitivity analysis is carried out to investigate the influence of impact conditions over target conditions, and vice versa. Finally, optimal parameters for the target conditions, for the given impact conditions, are arrived at as a design tool. The significance of various factors among both target and impact conditions are thus identified.