The local symmetry criterion predicts that cracks under mixed-mode loading will deflect so that the local Mode II stress intensity factor, kII, is zero. An efficient approach is presented for its implementation in finite element simulations of crack propagation, based on the observed linearity of kII over a wide range of deflection angles. This linearity is explained by expressing kII, for the kinked crack, in terms of the global stress intensity factors, KI and KII, and parallel T-stress, Sigma T, for the original straight crack. Deflection angles and crack paths obtained agreed with those obtained using a more cautious search algorithm, and with other deflection criteria. This has been particularly applicable to crack-growth simulations in graded materials, where elastic asymmetry results in mixed-mode loading