Abstract. A set of multivariate polynomials, over a field of zero or large characteristic, can be tested for algebraic independence by the well-known Jacobian criterion. For fields of other characteristic p > 0, there is no analogous characterization known. In this paper we give the first such criterion. Essentially, it boils down to a non-degeneracy condition on a lift of the Jacobian polynomial over (an unramified extension of) the ring of p-adic integers.Our proof builds on the de Rham-Witt complex, which was invented by Illusie (1979) for crystalline cohomology computations, and we deduce a natural generalization of the Jacobian. This new avatar we call the Witt-Jacobian. In essence, we show how to faithfully differentiate polynomials over Fp (i.e. somehow avoid ∂x p /∂x = 0) and thus capture algebraic independence.We apply the new criterion to put the problem of testing algebraic independence in the complexity class NP #P (previously best was PSPACE). Also, we give a modest application to the problem of identity testing in algebraic complexity theory.