File Vault: Deleted Files Still Encrypted?

This may be obvious, but I want to hear confirmation before I put this in practice. I've enabled File Vault on my MacBook. Works great, but since it's a laptop, I've been pretty obsessive about SRMing on delete to get rid of the data, not just delete it normally. It seems to me, now that everything is encryped, that when I delete a file, the system wouldn't bother to decrypt it on delete. So even my deleted files would requrie a password should my laptop fall into the wrong hands. This would make the secure delating surpurfulous. I've love to not do it anymore. Anybody have any thoughts on this subject?