  The potentials of spin-weighted wave equations in various Kerr-Newman black
holes are analyzed. They all form singular potential barriers at the event
horizon. Applying the WKB approximation it is shown that no particle can tunnel
out of the interior of a static black hole. However, photons inside a
non-extremely rotating Kerr black hole may tunnel out into the outer space,
whereas neutrinos, electrons, and gravitons may not. If the rotation is
extremal, any particle may tunnel out, under restrictive conditions. It is
unknown whether photons and gravitons may tunnel out if the black hole is
charged and rotating.
