IRS doesn't really care about the guy who died, his personal rep or the horse they rode in on.  They just want to process returns, especially if there is no tax to be collected.  Since IRS has to give Lacerte software its blessing, it doesn't seem to bother them, right?  If you want to save everyone, including the government, some time and trouble, go ahead and e-file with just the spouse's signature.  Have the PR sign a duplicate paper copy (or a Form 8879)  and keep it in your file if anyone asks later.  Or maybe attach the signature page as a pdf.