We present a group-theoretic criterion under which one may verify the Artin conjecture for some (non-monomial) Galois representations, up to finite height in the complex plane. In particular, the criterion applies to S 5 and A 5 representations. Under more general conditions, the technique allows for the possibility of verifying the Riemann hypothesis for Dedekind zeta functions of non-abelian extensions of Q.In addition, we discuss two methods for locating zeros of arbitrary L-functions. The first uses the explicit formula and techniques developed in [BS05] for computing with trace formulae. The second method generalizes that of Turing for verifying the Riemann hypothesis. In order to apply it we develop a rigorous algorithm for computing general L-functions on the critical line via the Fast Fourier Transform.Finally, we present some numerical results testing Artin's conjecture for S 5 representations, and the Riemann hypothesis for Dedekind zeta functions of S 5 and A 5 fields.1 Reading Turing's paper on the subject, which was his last, one marvels at what he accomplished with the limited computational resources of the day. His method was truly ahead of its time.