If anything, the fact that there was no semen present on the bodies,
plus the signs of non-penile vaginal penetration (a sexual assault
because at least some of it is performed while she is alive), 
indicate
that the killer is either too smart to leave physical evidence that
would form such a specific and distinctive link to him, is incapable 
of
normal sexual function (physical or psychological impotentence), or 
is
female...
 
 Perhaps he is to small to leave proof as a 'normal' penile inrustion.
 (Happi?)