Arthur's infinitesimal-character conjecture for congruence spectra

Let $G$ be a semisimple algebraic group over ${\mathbb Q}$, let $\Gamma$ be a congruence subgroup, and let $\pi$ be an irreducible representation of $G$ occurring weakly in $L^2(\Gamma\backslash G)$. An Arthur parameter is a parameter $\varphi_{\psi}$ arising from an Arthur parameter $\psi$. Arthur's infinitesimal-character conjecture. The infinitesimal character of $\pi$ is associated with an Arthur parameter $\varphi_{\psi}$. This is a deliberately weak formulation of Arthur's conjectures concerning the partition of the automorphic dual into finite Arthur packets; the source gives no resolution of this assertion.