assume and kill from Lisp?



When finding the Laplace transform:

  specint(t^(v-1)*exp(-a/t/4)*exp(-p*t),t);

It asks questions about the sign of p, a, and psey.  The questions for p 
and a are ok, but psey is an internal thing.  To do it's work, maxima 
has substituted psey for p, in case p is a more complicated expression.

Clearly, we don't want to ask about psey.  We should really be asking
about the sign of p and use that for psey.

How can that be done?  What I do right now is (asksign p) and based on 
the result, assume psey to be greater, less, or equal to 0.  I don't
do anything about psey afterwards because it's only used in one place
and a new assumption is done everytime psey is used.

This seems rather heavy-handed and somehow feels wrong.  What would be 
the right way to do this?

Ray