  A model is proposed to describe a transition from a charged black hole of
mass $M$ and charge $Q$ to one of mass $\bar{M}$ and charge $\bar{Q}$. The
basic equations are derived from the non-vacuum Einstein field equations
sourced by the Coulomb field and by a null scalar field with a nonvanishing
trace anomaly. It is shown that the nonvanishing trace of the energy-momentum
tensor prevents the formation of a naked singularity.
