See:
http://caselaw.lp.findlaw.com/scripts/getcase.pl?court=US&vol=000&invol=01-1757
But see:
http://www.crimblawg.com/2004/03/no_ex_post_fact.html
The question is whether change of statute of limitations period prior to expiry is an ex post facto violation. It is already SCOTUS law that a change of statute of limitations where the period expired is a violation.
Huh? I thought there wasn't a statute of limitations where murder was concerned?