We show that an étale motivic analogue of the Rost nilpotence principle holds for all smooth projective schemes over a perfect field. This provides a new approach to the question of Rost nilpotence and allows us to show that Rost nilpotence holds for surfaces, as well as for birationally ruled 3-folds over a field of characteristic 0. The talk is based on joint work with Andreas Rosenschon.