Each year, 320 000 people die from occupational injuries. The construction sector is one of the most hazardous sectors, showing a high incidence of workplace fatalities, of which many are caused by traumatic head injuries. In this study, the efficiency of construction helmets has been investigated through an in-depth accident reconstruction of a real-world workplace head trauma, aiming to investigate causation, prevention and liabilities in an ongoing police investigation. The accident was reconstructed with a state-of-the-art subject-specific head model, used to predict the skull fracture and the brain’s response to impact. The results of this study show how the skull fracture pattern was predicted with striking resemblance to the real-world fracture and how the locations of high brain strains were predicted in accordance with the victim’s brain lesions. The impact scenarios were compared with the hypothetical scenario in which a construction helmet was worn during the impact. The comparison provides evidence to support that a helmet would have prevented the skull fracture, and possibly also life-threatening brain injury. This case study demonstrates how FE reconstructions can help prove causality and liability in fatal head traumas. More importantly, the findings highlight the role of safety helmets in preventing lethal head injuries and their importance in combating the globally high incidence of fatal work-related accidents.