This work develops a generalized linear skull fracture criterion, the skull fracture correlate, SFC, applicable to impacts by flat targets on the skull in any angle. The SFC is the averaged acceleration over the HIC15 time interval based on data obtained from Hybrid-III headform impact tests. For 15% or less probability of skull fracture the threshold is SFC < 124 g, with a 95% confidence band of 96 < SFC < 144 g. The SFC correlation is established based on logistic regression against an extensive set of post mortem human specimen (PMHS) data. The biomechanical basis of SFC is validated by its good correlation with skull strain calculated using an anthropomorphic finite element model of the skull. This work is an extension and refinement of recent research results including the use of newly obtained PMHS data combined with historical data. Finite element model simulations were performed for all PMHS tests conducted for data comparison and statistical analysis.