This retrospective study of 80 cases of blunt head trauma with a determined cause (all occurred from 2000-2004 and are documented in Montreal lab records [Canada]) introduced a new definition of the hat-brim line, based on standard anatomical landmarks easily found on a dry skull. An inferior margin parallel to a line inspired by the Frankfort horizontal plane (horizontal plane passing through right and left porion points and the left orbitale) and passing through the center of the external auditory meatus was traced (EAM line). A superior margin parallel to a line inspired by the Frankfort horizontal plane and passing through the glabella was also traced (G line). Using these margins, two skull sections were defined: the area between the EAM line and the G line (hat-brim line) and the area located above the G line (above hat-brim line). Based on this new definition of the hat-brim line as the G-EAM zone, this study proposed the following criteria for distinguishing cranial wounds as blows or falls: localization of a wound above the G-EAM zone (hat-brim line) for blows; side lateralization: left for blows and right for falls; and higher number of lacerations for blows than for falls. The authors advise that these criteria should always be considered in relationship to the other autopsy finds and examination of the scene where the wound occurred. 3 tables, 1 figure, and 7 references