In ferroelectroelastic ceramics, the process of fracture is accompanied by significant inelastic deformation due to domain switching. This leads to an apparent toughening of the material, which is known as R-curve behavior. A promising approach to predict R-curves is based on one parameter fracture criteria. The scope of this paper is the examination of the physical validity of these criteria for realistic material behavior. Besides a general discussion of the problem, fracture of the lead zirconate titanate ceramic PIC151 is examined. Thereby, restriction is made to purely mechanical material behavior. The results indicate that the usage of one parameter fracture criteria is questionable. This is due to a conflict between the length scale of the zone wherein the asymptotic crack tip singularity dominates in the field solution of the continuum model and the length scale associated with the fracture process zone. It is concluded that an incorporation of the fracture process into the used fracture mechanics model is necessary to capture transient fracture of ferroelectroelastic ceramics properly.