  We study the high energy behaviour of fermions hitting a general wall caused
by a first-order phase transition. The wall profile is introduced through
general analytic and non-analytic functions. The reflection coefficient is
computed in the high energy limit and its connection with the analytic
properties of the wall profile function is shown. The high energy behaviour of
the fermions hitting the wall is determined either by the leading singularity,
i.e. the closest pole to the real axis, when the profile function is analytic,
or by the first non-continuous derivative on the real axis, in the non-analytic
case. CP-violating wall profiles are studied and it is shown that the
respective symmetry properties of the CP-conserving and CP-violating profile
functions plays an important role on the size of the CP asymmetry.
