Fracture toughness testing in the transition region often causes ductile tearing to precede cleavage fracture. The effect of ductile tearing on the fracture probability has in recent years become a subject of great interest. Brückner and Munz have developed a Weibull statistics based model to describe this effect. In this paper a similar model, based on the WST-model, is derived. The model is applied to several different sets of brittle fracture data. The differences between the present model and the B & M model is discussed. Finally the effect of loss of constraint on the models is noted.