On Euler Characteristic of equivariant sheaves

Let $k$ be an algebraically closed field of characteristic $p>0$ and let $\ell$ be another prime number. O. Gabber and F. Loeser proved that for any algebraic torus $T$ over $k$ and any perverse $\ell$-adic sheaf \calF on $T$ the Euler characteristic \chi(\calF) is non-negative. We conjecture that the same result holds for any perverse sheaf \calF on a reductive group $G$ over $k$ which is equivariant with respect to the adjoint action. We prove the conjecture when \calF is obtained by Goresky-MacPherson extension from the set of regular semi-simple elements in $G$. From this we deduce that the conjecture holds for $G$ of semi-simple rank 1