Deleting expired certificates from the security file.
Can I delete expired certificates from the CA Top Secret Security File?
Release: TOPSEC00200-15-Top Secret-Security
If certificates are already expired, they are treated as if they don't exist.
If a security call is issued to read the digital certificate, CA Top Secret will pass back a not found condition even though they are on the keyring and on the CA Top Secret Security File.
So, deleting a certificate that have already expired, should not cause any problems.