  The temperature dependence of the electron spin life-time, T_1 and the
g-factor are anomalous in alkali fullerides (K,Rb)_3C_60, which cannot be
explained by the canonical Elliott-Yafet theory. These materials are archetypes
of strongly correlated and narrow band metals. We introduce the concept of
"complex electron spin resonance frequency shift" to treat these measurables in
a unified manner within the Kubo formalism. The theory is applicable for metals
with nearly degenerate conduction bands and large momentum scattering even with
an anomalous temperature dependence and sizeable residual value.
