Letbe a free product and Out( ) the outer automorphism group of . In this article using the theory of laminations we give a criterion for a subgroup À of Out( ) to contain a nonabelian free subgroup. We also study the centraliser of an iwip element of Out( ) and the stabiliser of its associated lamination.

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Let G be a finitely generated free-by-finite group. We show that the group Out(G) of outer automorphisms of G is translation discrete and satisfies the strong Tits alternative.